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Objective: To investigate the clinicopathological and molecular genetic characteristics of intracranial mesenchymal tumors with FET::CREB fusion transcript. Methods: The clinical and imaging data of 6 cases of intracranial mesenchymal tumors with FET::CREB fusion from December 2018 to December 2023 were collected at the First Affiliated Hospital of Zhengzhou University. Their histological features, immunophenotype and molecular characteristics were analyzed. Results: Among the 6 patients, 4 were males and 2 were females, and the median age was 20 years. The clinical symptoms were increased intracranial pressure in 5 cases and epilepsy in 1 case. The lesion sites were cerebellum (2 cases), frontal lobe (2 cases), parietal lobe (1 case), and cranioorbital communication (1 case). The radiological features mainly showed solid or cystic components, with obvious annular enhancement on MRI. The histopathological features showed a wide spectrum of morphology, clear boundaries and fibrous pseudocapsule. The tumor cells were arranged in a lamellar or nodular pattern, and some in cord or loose network. The tumor cells were spindle, oval, epithelioid or stellate. The stroma was collagenous or mucin-rich, and accompanied by abundant lymphocytes and plasma cells infiltration. By immunohistochemical staining, desmin, CD99 and EMA were expressed in 6 cases, CD68 in 1 case, MUC4 in 1 case, synaptophysin in 2 cases, and ALK in 1 case. The Ki-67 proliferation index was between 1%-15%. Molecular analysis showed EWSR1::ATF1 fusion in 3 cases, EWSR1::CREB1 fusion in 2 cases, and EWSR1::CREM fusion in 1 case. Conclusions: Intracranial mesenchymal tumors with FET::CREB fusion are relatively rare and typically occur in children and younger adults. These tumors have a broad morphological spectrum and often express desmin, CD99 and EMA. The molecular characteristics are the gene fusions of FET family (mainly EWSR1, FUS) with CREB family transcription factors (ATF1, CREB1 or CREM). It is necessary to distinguish these tumors from meningiomas and solitary fibrous tumors, and the combination of immunohistochemical staining and molecular genetic testing can effectively help identify these tumors.

FUS::CREM fusion is a distinct primary driver in rare neoplasms of the head and neck and other anatomic sites. Herein, we describe the clinicopathological, imaging, and molecular features of a malignant epithelioid mesenchymal neoplasm harboring FUS::CREM fusion, arising in the tongue of a 46-year-old male. Clinically, the patient presented with a left upper neck mass. Imaging revealed a 4.0 cm mass at the left base of tongue. Histologically, the tumor consisted of sheets of loosely cohesive, small round to ovoid cells with moderate cytoplasm, small nuclei with coarse chromatin, frequent nuclear pseudoinclusions, and dense peripheral lymphoplasmacytic and histiocytic infiltrates. Malignant features, including tumor necrosis, perineural invasion, and increased mitotic activity were observed; however, lymphovascular invasion was absent with no evidence metastatic disease in the examined lymph nodes. A comprehensive panel of immunohistochemical stains showed positivity for synaptophysin and ALK, with negative results for all other markers. RNA-based next-generation sequencing using anchored multiplex polymerase chain reaction (PCR) was performed and detected FUS::CREM fusion gene. The patient was treated by excision and postsurgical chemoradiation with no evidence of recurrence after four months. Additional cases supported by comprehensive clinical data collected over an extended period are necessary to precisely characterize epithelioid mesenchymal neoplasms harboring FUS::CREM fusion in the head and neck., (© 2024. The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.)

BACKGROUND Phosphaturic mesenchymal tumor (PMT) is an extremely rare mesenchymal neoplasm that is commonly seen in bone and soft tissue. It is associated with a paraneoplastic syndrome, oncogenic osteomalacia, due to tumor-induced urinary phosphate wasting. It is demonstrated to be predominantly mediated by fibroblast growth factor 23 (FGF23)/fibroblast growth factor receptor 1 (FGFR1) axis. Clinically, PMT usually presents as a solitary lesion in the bone. The diagnosis of PMT is challenging due to its non-specific clinical manifestation, radiologic findings, and morphological features. CASE REPORT We report the case of a 50-year-old man presenting with multiple lytic bone lesions and associated pathologic fracture of the right femur, clinically suspicious for multiple myeloma or other metastatic malignant process. Resection from the right femur showed a hypercellular lesion composed of oval-to-spindled cells infiltrating the native trabecular bone with admixed multinucleated giant cells. Immunohistochemical (IHC) staining and in situ hybridization (ISH) demonstrated the tumor cells were positive for SATB2, ERG, FGFR1, and FGF23 ISH. DNA and RNA next-generation sequencing showed marked increases in mRNA levels of FGF23 and FGFR1. The constellation of clinicoradiologic, histomorphologic, IHC, and molecular findings supported a diagnosis of primary benign PMT. CONCLUSIONS This case report discusses a patient with PMT presenting with multifocal lesions due to tumor-induced osteomalacia at initial presentation. We hope that this report will increase the awareness of clinician and pathologists of PMT as a differential diagnosis in patients presenting with multifocal lytic bone lesions. In turn, this will prevent misdiagnosis and overtreatment of a typically benign process.

Phosphaturic mesenchymal tumors (PMT) are uncommon neoplasms that cause hypophosphatemia/osteomalacia mainly by secreting fibroblast growth factor 23. We previously identified FN1::FGFR1/FGF1 fusions in nearly half of the PMTs and frequent KL (Klotho or α-Klotho) overexpression in only those with no known fusion. Here, we studied a larger cohort of PMTs for KL expression and alterations. By FN1 break-apart fluorescence in situ hybridization (FISH) and reappraisal of previous RNA sequencing data, 6 tumors previously considered "fusion-negative" (defined by negative results of FISH for FN1::FGFR1 fusion and FGF1 break-apart and/or of RNA sequencing) were reclassified as fusion-positive PMTs, including 1 containing a novel FN1::ZACN fusion. The final cohort of fusion-negative PMTs included 33 tumors from 32 patients, which occurred in the bone (n = 18), soft tissue (n = 10), sinonasal tract (n = 4), and brain (n = 1). In combination with previous work, RNA sequencing, RNA in situ hybridization, and immunohistochemistry showed largely concordant results and demonstrated KL/α-Klotho overexpression in 17 of the 28 fusion-negative and none of the 10 fusion-positive PMTs studied. Prompted by a patient in this cohort harboring germline KL upstream translocation with systemic α-Klotho overexpression and multifocal PMTs, FISH was performed and revealed KL rearrangement in 16 of the 33 fusion-negative PMTs (one also with amplification), including 14 of the 17 cases with KL/α-Klotho overexpression and none of the 11 KL/α-Klotho-low fusion-negative and 11 fusion-positive cases studied. Whole genomic sequencing confirmed translocation and inversion in 2 FISH-positive cases involving the KL upstream region, warranting further investigation into the mechanism whereby these rearrangements may lead to KL upregulation. Methylated DNA immunoprecipitation and sequencing suggested no major role of promoter methylation in KL regulation in PMT. Interestingly, KL-high/-rearranged cases seemed to form a clinicopathologically homogeneous group, showing a predilection for skeletal/sinonasal locations and typically matrix-poor, cellular solitary fibrous tumor-like morphology. Importantly, FGFR1 signaling pathways were upregulated in fusion-negative PMTs regardless of the KL status compared with non-PMT mesenchymal tumors by gene set enrichment analysis, perhaps justifying FGFR1 inhibition in treating this subset of PMTs., (Copyright © 2023 United States & Canadian Academy of Pathology. Published by Elsevier Inc. All rights reserved.)

Mesenchymal neoplasms with GLI1 alterations (rearrangements and/or amplification) have been reported recently in several anatomic locations, which include head and neck, soft tissue, and gastrointestinal tract. Herein, to the best of our knowledge, we describe the first three cases of superficial/subcutaneous mesenchymal neoplasm with GLI1 amplification. The neoplasms exhibited low-grade cytologic features with predominant round cell morphology, glomangioma-like areas and a rich background capillary network. There were two to three mitotic figures per 10 HPF and focal necrosis in one case. The tumors exhibited variable expression of CDK4, MDM2, STAT6, D2-40, CD56 and cyclin D1. p16 had strong and diffuse nuclear and cytoplasmic expression in two cases. Numerous other stains were negative. Fluorescence in situ hybridization detected GLI1, DDIT3, and CDK4 coamplification in all cases, while next generation sequencing did not detect a GLI1 gene fusion. The overall features were compatible with a GLI1-amplified mesenchymal neoplasm. In Case 1 a new distant skin lesion appeared 1 month after the surgery exhibiting similar morphology albeit with a higher mitotic index. In Cases 2 and 3, there is no evidence of local recurrence or systemic disease after 8 years and 1 month of follow-up, respectively. These new cases of superficial GLI1-amplified neoplasm expand its clinical spectrum and enter the realm of dermatopathology. The combination of CDK4, cyclin D1, D2-40, and p16 expression with variable MDM2, STAT6, CD56, and S100 immunoreactivity in a low-grade neoplasm with round/ovoid cytomorphology resembling a vascular or adnexal neoplasm may suggest the possibility of GLI1-amplified neoplasm., (© 2022 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Ectomesenchymoma is an exceedingly rare biphasic malignant tumor characterized by the presence of mesenchymal and neuroectodermal elements. The majority of patients are infants or children. We describe the first case of this entity diagnosed as a primary uterine tumor. A 72-year-old female presented with post-menopausal bleeding. Dilatation and curettage showed irregular mesenchymal proliferation of uncertain nature. In the hysterectomy specimen, a myxoid spindle cell tumor with areas of skeletal muscle and neural differentiation was found in the uterus, with direct invasion of the small intestine, and biphasic differentiation into rhabdomyosarcoma and ganglioneuroblastoma was unequivocally seen in a lymph node metastasis. The morphological findings were validated by immunohistochemistry. Massive parallel sequencing identified TP53, PTEN, and DICER1 mutations in the tumor. This report describes the presence of ectomesenchymoma in an unusual primary organ and in an uncharacteristic age and presents novel data regarding the genetic characteristics of this tumor., (© 2021. The Author(s).)

Cutaneous anaplastic large-cell lymphoma (C-ALCL) represents one of the entities within the group of CD30-positive lymphoproliferative disorders of the skin. Most cases are ALK-negative, though isolated cases of ALK-positive C-ALCL have also been reported. By definition, the diagnosis of C-ALCL requires the expression of CD30 in >75% of the cells. Histopathologically, C-ALCL shows a dermal-based nodular and circumscribed proliferation of large pleomorphic cells with vesicular nuclei, prominent nucleoli, and eosinophilic cytoplasm, including hallmark cells. Since 1990, isolated case reports of a so-called "sarcomatoid" variant have been published in the literature. Herein, we present a series of 11 cases of spindle (sarcomatoid) C-ALCL, with comprehensive histopathologic, immunophenotypic, and molecular data. Spindle C-ALCL represents a potential mimicker of malignant mesenchymal or hematopoietic tumors in the skin and should always be considered in the differential diagnosis when assessing cutaneous pleomorphic spindle cell neoplasms., Competing Interests: Conflicts of Interest and Source of Funding: The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Phosphaturic mesenchymal tumors (PMT) are rare neoplasms characterized by secretion of FGF23, resulting in renal phosphate wasting and osteomalacia. This tumor-induced osteomalacia (TIO) is cured by complete resection; thus, diagnosis is important, particularly on biopsy. Although PMT have a classic histologic appearance of bland spindled cells with conspicuous vascular network and characteristic smudgy basophilic matrix, there is a broad histologic spectrum and variant histologic patterns can make recognition difficult. Recent studies have demonstrated FN1-FGFR1 and FN1-FGF1 gene fusions in PMT; however, approximately 50% of cases are negative for these fusions. We sought to characterize 6 cases of PMT in-depth, compare fusion detection methods, and determine whether alternative fusions could be uncovered by targeted RNA sequencing. Of the 6 cases of PMT in our institutional archive, 3 were not given diagnoses of PMT at the time of initial pathologic examination. We characterized the immunoprofile (SMA, D2-40, CD56, S100 protein, desmin, SATB2, and ERG) and gene fusion status (FN1 and FGFR1 rearrangements by fluorescent in situ hybridization (FISH) and two targeted RNA sequencing approaches) in these cases. Tumors were consistently positive for SATB2 and negative for desmin, with 5/6 cases expressing ERG and CD56. One specimen was acid-decalcified and failed FISH and RNA sequencing. We found FN1 gene rearrangements by FISH in 2/5 cases, and a FN1-FGFR1 fusion by targeted RNA sequencing. No alternative gene fusions were identified by RNA sequencing. Our findings suggest that IHC and molecular analysis can aid in the diagnosis of PMT, guiding excision of the tumor and resolution of osteomalacia.

To our knowledge, we describe the first mesenchymal tumor with a novel GLI1-FOXO4 fusion gene. This well-circumscribed kidney tumor displayed variably myxoid and epithelioid histologic features with a focally nodular growth pattern. The tumor cells showed bland, round to ovoid nuclei, with no overt high-grade features. The tumor showed focal immunopositivity for smooth muscle actin and Melan-A, which raised the possibility of a relationship with a perivascular epithelioid cell tumor. The clinical and morphologic features appear distinct from other reported neoplasms harboring GLI1 or FOXO4 gene rearrangements. The patient underwent radical nephrectomy and is without evidence of disease during a relatively short clinical follow-up period. However, the features of this tumor likely warrant long-term follow-up to monitor for the possibility of a late recurrence or metastasis. In addition to reporting this novel fusion-positive tumor, we also provide a brief review of GLI1 and FOXO4 gene functions in both normal and neoplastic contexts., (© 2020 Wiley Periodicals LLC.)

Synovial sarcoma (SS) is a malignant mesenchymal soft tissue neoplasm. Despite its name, the cells of origin are not synovial cells, but rather neural, myogenic, or multipotent mesenchymal stem cells have been proposed as possible cells originators. Unlike other sarcomas, an unusual presentation of long-term pain at the tumor site has been documented, but the exact mechanisms have not been fully clarified yet. The transient receptor potential ankyrin 1 (TRPA1) is a nonselective cation channel mainly expressed in primary sensory neurons, where it functions as a pain sensor. TRPA1 have also been described in multiple non-excitable cells, including those derived from neural crest stem cells such as glial cells and, in particular, Schwann cell oligodendrocytes and astrocytes. We evaluated TRPA1 expression in SS. We selected a cohort of 41 SSs, and by immunohistochemistry, we studied TRPA1 expression . TRPA1 was found in 92.6% of cases. Triple TRPA1/pS100/SOX10 and TRPA1/SLUG/SNAIL staining strongly supports a neural origin of SS. TRPA1 positivity was also observed in a subset of cases negative with pS100, SOX10 and/or SLUG/SNAIL, and these divergent phenotypes may reflect a process of tumor plasticity and dedifferentiation of neural-derived SSs. Given the functional diversity of TRPA1 and its expression in neuronal and non-neuronal multipotent neural crest stem cells, it remains to be determined whether TRPA1 expression in SSs neoplastic cells plays a role in the molecular mechanism associated with premonitory pain symptoms and tumor progression.

Aims: Ectomesenchymal chondromyxoid tumour (ECT) is a rare benign intraoral tumour which almost exclusively presents as a small mass of the anterior dorsal tongue. Recently, the RREB1-MRTFB (previously known as MKL2) fusion gene has been identified in 90% of ECTs, all located in the tongue, emphasising its genetic distinctiveness. Here, we report two mesenchymal tumours involving the superior mediastinum of adult women with RREB1-MRTFB fusions., Methods and Results: Both tumours presented as well-circumscribed paravertebral masses that were clinically suspected to be schwannoma. After fragmented resection, recurrence was not observed at 27 and 18 months. Although tumours were originally unclassifiable, next-generation sequencing detected identical RREB1 (exon 8)-MRTFB (exon 11) fusion transcripts, which were validated by reverse transcriptase-polymerase chain reaction, Sanger sequencing, and fluorescence in-situ hybridisation. Both tumours shared hyalinised areas with round cells embedded in a cord or reticular manner. The tumour cells showed mild nuclear atypia of possible degenerative type with very low mitotic activity, and were at least focally positive for S100, glial fibrillary acidic protein, smooth muscle actin and epithelial membrane antigen. Overall, these findings suggest that they may represent previously undescribed extra-glossal ECT involving the mediastinum. However, the histology was not classic for ECT, because that in case 2 was predominated by storiform growth of spindle cells, whereas the tumour in case 1 lacked myxoid change., Conclusions: We have provided the first evidence that RREB1-MRTFB fusion is not limited to tumours in the head region, and whether such tumours represent extra-glossal ECTs requires further research., (© 2020 John Wiley & Sons Ltd.)

Based on our current knowledge, 5-10% of all malignancies are part of hereditary cancer syndromes. Although the increasing diagnostic role of molecular genetic testing makes us able to recognize more hereditary cancer patients, the careful exploration of family and clinical history by physicians is still the most important step for the diagnosis. In our review we deal with mesenchymal tumours associated with hereditary syndromes. Sarcomas comprise only 1% of all malignancies, but they often associate with familiar diseases so they can serve as an indicator of these syndromes. The diagnosis of hereditary cancer predisposition syndromes is essential to ensure appropriate therapy and follow-up for our patients.

Conventional osteosarcoma is the most common primary malignancy of bone. This group of neoplasms is subclassified according to specific histological features, but hitherto there has been no correlation between subtype, treatment, and prognosis. By in-depth genetic analyses of a chondroblastoma-like osteosarcoma, we detect a genetic profile that is distinct from those previously reported in benign and malignant bone tumors. The overall genomic copy number profile was less complex than that typically associated with conventional osteosarcoma, and there was no activating point mutation in any of H3F3A, H3F3B, IDH1, IDH2, BRAF, or GNAS. Instead, we found a homozygous CDKN2A deletion, a DMD microdeletion and an FN1-FGFR1 gene fusion. The latter alteration has been described in phosphaturic mesenchymal tumor. This tumor type shares some morphological features with chondroblastoma-like osteosarcoma and we cannot rule out that the present case actually represents an FN1-FGFR1 positive malignant phosphaturic mesenchymal tumor of bone without osteomalacia., (© 2019 Wiley Periodicals, Inc.)

Perhaps the rarest cause of osteomalacia is that caused by a neoplasm, so-called "tumor-induced osteomalacia" (TIO). Although very rare cases of TIO have been associated with carcinomas and syndromes such as neurofibromatosis type-1 and McCune-Albright syndrome, the overwhelming majority of TIO is caused by tumors of mesenchymal origin. Although it was historically felt that almost any mesenchymal tumor type could occasionally result in TIO, it has become increasingly clear over the past several decades that almost all cases of mesenchymal tumor-associated TIO are caused by a single entity, known as "phosphaturic mesenchymal tumor" (PMT). This article will review historical aspects of this tumor, as well as its clinical, morphological, immunohistochemical and molecular genetic features. The distinction of PMT from its many potential morphological mimics is discussed in detail., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Prognostication in mesenchymal tumors can be challenging. They exhibit diverse, and sometimes overlapping, histologic features that are not always predictive of their true behavior. This article highlights examples of both traditional and emerging sarcoma biomarkers., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Among the various genes that can be rearranged in soft tissue neoplasms associated with nonrandom chromosomal translocations, EWSR1 is the most frequent one to partner with other genes to generate recurrent fusion genes. This leads to a spectrum of clinically and pathologically diverse mesenchymal and nonmesenchymal neoplasms, variably manifesting as small round cell, spindle cell, clear cell or adipocytic tumors, or tumors with distinctive myxoid stroma. This review summarizes the growing list of mesenchymal neoplasms that are associated with EWSR1 gene rearrangements., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Pediatric soft tissue tumors are relatively rare and show significant overlap in morphology and immunoprofile, often posing diagnostic and management challenges. Thus, their classification remains often subjective or lumped under "unclassified categories," as a number of lesions lack objective and reproducible criteria in diagnosis. Although in a subset of cases immunohistochemistry has been proved useful to identify a specific line of differentiation, most tumors lack a readily defined histogenesis, being characterized by a rather non-specific immunoprofile. Furthermore, tumors with an ambiguous diagnosis are difficult to grade and their risk of malignancy or clinical management remains uncertain. Advances in molecular genetics, including the more wide application of next generation sequencing in routine clinical practice, have improved diagnosis and refined classification based on objective molecular markers. Importantly, some soft tissue tumors in children are characterized by recurrent gene fusions involving either growth factors (eg, PDGFB) or protein kinases (eg, ALK, ROS, NTRK, BRAF), which have paved the way for new targeted treatments that block the respective upregulated downstream pathways. However, the majority of gene fusions or mutations detected in soft tissue tumors result in an abnormal function of transcription factors or chromatin remodeling. The present review focuses on the latest genetic discoveries in the spectrum of both benign and malignant pediatric soft tissue neoplasia. These genetic abnormalities promise to provide relevant insight for their proper classification, prognosis, and treatment. The entities discussed herein are grouped either based on their shared genetic mechanism or based on their presumed line of differentiation., (© 2018 Wiley Periodicals, Inc.)

Mesenchymal neoplasms of the genitourinary (GU) tract often pose considerable diagnostic challenges due to their wide morphologic spectrum, relative rarity, and unexpected incidence at GU sites. Soft tissue tumors arise throughout the GU tract, whether from adventitia surrounding or connective tissues within the kidneys, urinary bladder, and male and female genital organs. This selected article focuses on a subset of these lesions, ranging from benign to malignant and encompassing a range of patterns of mesenchymal differentiation, where recent scholarship has lent greater insight into their clinical, molecular, or diagnostic features., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Aims: Phosphaturic mesenchymal tumour, mixed connective tissue variant (PMT-MCT), is a tumour of uncertain differentiation, characterised by 'smudgy/grungy' calcification and vitamin D-resistant phosphaturic osteomalacia. Fibroblast growth factor (FGF)23 is recognised as a reliable marker of PMT-MCT, but quantitative evaluation has never been performed. We reviewed cases of tumour-associated osteomalacia or histologically definitive PMT-MCT without osteomalacia using histological, immunohistochemical and genetic methods and evaluated the diagnostic significance of these findings., Methods and Results: A total of 19 tumours from 14 cases diagnosed previously as PMT-MCT were retrieved, on which immunohistochemical staining, reverse transcription-polymerase chain reaction (RT-PCR) and fluorescence in-situ hybridisation (FISH) analysis were performed. Histologically, fibrous capsule, calcification and giant cell reaction tended to be observed in soft-tissue PMT-MCT, while PMT-MCT of bone and multiple PMT-MCT showed an infiltrative growth pattern. The immunohistochemical results were as follows: the tumour cells were positive for FGF23 (nine of 12, 75%), FGFR1 (11 of 11, 100%), CD56 (12 of 14, 85.7%) and E26 oncogene homologue (ERG) (5 of 13, 38.4%). The sole malignant tumour was positive for p53. FGF23 mRNA was detected in seven of 14 formalin-fixed paraffin-embedded (FFPE) specimens and all five frozen specimens by RT-PCR. The level of FGF23 mRNA, which was determined by real-time PCR, varied among the phosphaturic cases. Two of 17 tumours were positive for FGFR1 gene rearrangement., Conclusions: It was considered that PMT-MCT is a histopathological entity with or without phosphaturia, with varying levels of FGF23 mRNA, and with or without fibronectin 1 (FN1)-FGFR1 fusion gene. The authors propose that the histology of PMT-MCT differs depending on its location, such as bone or soft tissue, which could complicate the differential diagnosis., (© 2017 John Wiley & Sons Ltd.)

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm of uncertain histogenesis that has been linked to tumor-induced osteomalacia (TIO) since 1959. The neoplastic cells produce increased amount of FGF23 which results in TIO via uncontrolled renal loss of phosphate (phosphaturia), and consequently diminished bone mineralization. To date, ∼300 cases have been reported. Although there is increasing evidence that PMT can be diagnosed by reproducible histopathologic features, firm diagnosis has been often restricted to cases associated with TIO and, hence, diagnosis of "nonphosphaturic variants" remained challenging. Recently, FGFR1/FN1 gene fusions were detected in roughly half of cases. We herein reviewed the clinicopathologic features of 22 PMTs (15 cases not published before), stained them with an extended immunohistochemical marker panel and examined them by fluorescence in situ hybridization for FGFR1 gene fusions. Patients were 12 males and 9 females (one of unknown sex) aged 33 to 83 years (median: 52 y). Lesions affected the soft tissues (n=11), bones (n=6), sinonasal tract (n=4), and unspecified site (n=1). Most lesions originated in the extremities (9 in the lower and 4 in the upper extremities). Acral sites were involved in 10 patients (6 foot/heel, 3 fingers/hands, and 1 in unspecified digit). Phosphaturia and TIO were recorded in 10/11 and 9/14 patients with detailed clinical data, respectively. Limited follow-up (5 mo to 14 y; median: 16 mo) was available for 14 patients. Local recurrence was noted in one patient and metastasis in another patient. Histologically, 11 tumors were purely of conventional mixed connective tissue type, 3 were chondromyxoid fibroma-like, 2 were hemangio-/glomangiopericytoma-like with giant cells, and 1 case each angiomyolipoma-like and reparative giant cell granuloma-like. Four tumors contained admixture of patterns (predominantly cellular with variable conventional component). Immunohistochemistry showed consistent expression of CD56 (11/11; 100%), ERG (19/21; 90%), SATB2 (19/21; 90%), and somatostatin receptor 2A (15/19; 79%), while other markers tested negative: DOG1 (0/17), beta-catenin (0/14), S100 protein (0/14), and STAT6 (0/7). FGFR1 fluorescence in situ hybridization was positive in 8/17 (47%) evaluable cases. These results add to the phenotypic delineation of PMT reporting for the first time consistent expression of SATB2 and excluding any phenotypic overlap with solitary fibrous tumor or sinonasal glomangiopericytoma. The unifying immunophenotype of the neoplastic cells irrespective of the histologic pattern suggests a specific disease entity with diverse morphotypes/variants rather than different neoplasms unified by TIO.

Aims: Fibrocartilaginous mesenchymoma is a rare intraosseous lesion, with a total of 26 cases described in the literature. This study describes the clinical, radiological and histological features of eight new cases of fibrocartilaginous mesenchymoma collected at a single institution between 1982 and 2016. The presence of GNAS and IDH1/2 mutations and MDM2 amplification was explored to evaluate possible links between fibrocartilaginous mesenchymoma, fibrous dysplasia, de-differentiated chondrosarcoma and low-grade osteosarcoma., Methods and Results: Eight new cases of fibrocartilaginous mesenchymoma of bone identified in our archives, dating from 1982 to 2016, were reviewed. The diagnosis was not performed on the initial biopsy in any of these cases, due mainly to the absence of obvious cartilaginous differentiation. On imaging, the tumour contained cartilaginous calcifications and showed a very strong uptake of contrast medium after injection. Histologically, the tumour was characterized by spindle cell proliferation mimicking a low-grade spindle cell sarcoma, associated with epiphyseal growth-plate-like nodules of cartilage and bone production. Molecularly, no GNAS and IDH1/2 mutations or MDM2 amplification were found in the cases analysed. Only one case recurred 1 year following intralesional resection. None died of disease., Conclusions: This very rare bone tumour has a typical radiological and histological pattern and a favourable survival outcome after treatment. Local recurrences can be prevented with complete surgery. Fibrocartilaginous mesenchymoma does not seem to be related genetically to fibrous dysplasia, low-grade osteosarcoma and de-differentiated chondrosarcoma., (© 2017 John Wiley & Sons Ltd.)

Objective: Programmed death ligand 1 (PD-L1) found on tumor cells has recently been reported to have a key role in the development and dissemination of many tumors, such as lung and breast carcinomas. In this study, we retrospectively analyzed PD-L1 expression among different types of sarcomas., Material and Method: Tissue microarrays of 3-4 mm diameter were composed from paraffin blocks of 222 various sarcomas. Slides prepared from microarrays were stained for PD-L1 antibody (Cell Signaling, E1L3N®) using Leica Bond Autostainer. Any membranous staining over 5% of the cells was regarded as positive. Quantitative real-time PCR with TaqMan gene expression assays for PDL1 was performed using whole sections from FFPE tissue of PD-L1 positive cases, by normalizing absolute values to β-actin. Relative expression level of mRNA of PDL1 was calculated and scored using Log102(threshold cycle of b-actin - threshold cycle of PDL1)., Results: Immunohistochemically, PD-L1 expression was present in 34 of 222 (15%) sarcomas. 5/13 (39%) undifferentiated pleomorphic sarcomas, 6/18 (33%) malignant peripheral nerve sheath tumors, 5/16 (31%) dedifferentiated liposarcomas, 4/19 (21%) rhabdomyosarcomas, 2/16 (13%) epithelioid sarcomas, 2/15 (13%) leiomyosarcomas, 3/26 (12%) synovial sarcomas, 1/18 (6%) myxoid liposarcoma, 1/2 (50%) extraskeletal myxoid chondrosarcoma, 1/3 (33%) alveolar soft part sarcoma, 1/3 (33%) parachordoma/myoepithelioma, 1/5 (20%) pleomorphic liposarcoma, 1/7 (14%) angiosarcoma, 1/8 (13%) Ewing sarcoma showed PD-L1 expression. Cases of solitary fibrous tumor/hemangiopericytoma (18), desmoplastic round cell tumor (14), Ewing-like sarcoma (6), epithelioid hemangioendothelioma (5), clear cell sarcoma (4), myxofibrosarcoma (4), low grade fibromyxoid sarcoma (2) were all negative. Tumor-infiltrating hematopoietic cells were positive for PD-L1 in 32 cases (15%) with only 2 cases overlapping with PD-L1 staining in tumoral cells. Sixteen of 34 (47%) immunohistochemically PD-L1 positive cases showed significant but low-level PD-L1 mRNA overexpression., Conclusion: We have shown PD-L1 expression in a subset of sarcomas, both at the protein and mRNA level. High-grade pleomorphic sarcomas tend to show more frequent PD-L1 expression. Clinical trials are necessary to further assess the effect of anti PD-L1 drugs on sarcomas showing PD-L1 expression.

Introduction: Sarcomas are rare uterine tumors with leiomyosarcomas and endometrial stromal sarcomas constituting the predominant entities often making their first appearance in young and middle-aged women. By histology combined with immunostaining alone some of these tumors can offer diagnostic challenges e.g. for the differential diagnosis between leiomyosarcomas and smooth muscle tumors of uncertain malignant potential (STUMP). Areas covered: Recent advances in the genetic classification and subclassification, respectively, have shown that genetic markers can offer a valuable adjunct to conventional diagnostic tools. Herein, we will review these recent data from the literature also referring to genetic alterations found in STUMP, endometrial stromal nodules, and leiomyomas including their variants. Expert commentary: For the future, we consider genetic classification as a necessary step in the clinical management of these tumors which will help not only to improve the diagnosis but also the therapy of these malignancies often associated with a worse prognosis.

Glioblastomas are characterized by transcriptionally distinct subtypes, but despite possible clinical relevance, their regulation remains poorly understood. The commonly used molecular classification systems for GBM all identify a subtype with high expression of mesenchymal marker transcripts, strongly associated with invasive growth. We used a comprehensive data-driven network modeling technique (augmented sparse inverse covariance selection, aSICS) to define separate genomic, epigenetic, and transcriptional regulators of glioblastoma subtypes. Our model identified Annexin A2 (ANXA2) as a novel methylation-controlled positive regulator of the mesenchymal subtype. Subsequent evaluation in two independent cohorts established ANXA2 expression as a prognostic factor that is dependent on ANXA2 promoter methylation. ANXA2 knockdown in primary glioblastoma stem cell-like cultures suppressed known mesenchymal master regulators, and abrogated cell proliferation and invasion. Our results place ANXA2 at the apex of a regulatory cascade that determines glioblastoma mesenchymal transformation and validate aSICS as a general methodology to uncover regulators of cancer subtypes., (Copyright © 2016. Published by Elsevier B.V.)

Phosphaturic mesenchymal tumor (PMT) is a rare neoplasm; however, it is the most common cause of tumor-induced osteomalacia (TIO), a paraneoplastic syndrome characterized by renal phosphate wasting and hypophosphatemia. A subset of PMTs harbours an FGFR1 translocation although this alteration has not been demonstrated in PMT involving a head and neck site. We present a series of five PMTs involving the head and neck and demonstrate the diagnostic utility of fluorescence in situ hybridization (FISH) for detecting FGFR1 translocations. Patients' age and sex, tumor location, original diagnosis, the duration of symptoms, the presence of TIO, biochemical results, and medical management were reviewed. The median age at presentation was 45 (range, 24-58 years) and TIO was present in three cases. Four tumors involved soft tissue and one involved bone. Four out of the five tumors in our series were initially misdiagnosed. Three tumors were ultimately categorized as malignant PMT (two patients developed metastatic disease). FGFR1 translocation was present in two out of four cases and remained unknown in one case. In summary, we report on five cases of PMTs arising in the head and neck and confirm utility of FGFR1 FISH in the diagnosis of a subset of PMT.

Malignant ectomesenchymoma (MEM) is an exceedingly rare pediatric sarcoma with a predilection for infants and young children and is composed of dual malignant mesenchymal and neuroectodermal components. Microscopically, MEM displays areas of rhabdomyosarcoma (RMS) with intermixed neuronal/neuroblastic foci. The molecular alterations associated with MEM and its relationship with embryonal RMS (ERMS) and malignant peripheral nerve sheath tumor (MPNST) have not yet been elucidated. In this study we used whole-transcriptome sequencing in 2 MEM index cases with available frozen tissue, followed by screening of the identified genetic abnormalities in 5 additional cases. No candidate fusion genes were detected by FusionSeq analysis; however, the mutation detection algorithms revealed HRAS and PTPRD hotspot mutations in both index cases, with 1 case harboring an additional FBXW7 mutation. As these mutation profiles have been previously described in ERMS we have tested their incidence in a control group of 7 age-matched ERMS. In addition, the gene signature of MEM was compared with that of RMS, MPNST, and neuronal lineage. All 7 MEM patients were male, with a mean age of 7.5 months (range, 0.6 to 17 mo). All except 1 occurred in the pelvic/urogenital region. Most cases showed ERMS elements, with occasional spindle or undifferentiated/round cell areas. The intermixed neuroectodermal components were mostly scattered ganglion cells, ganglioneuroma, or ganglioneuroblastoma. By Sanger sequencing, 6 of 7 (86%) MEMs had HRAS mutations, with no additional case harboring PTPRD or FBXW7 mutations. The only case lacking HRAS mutation showed neuroblastic micronodules without ganglion cells. The trimethylation at lysine 27 of histone H3 (H3K27me3) expression, typically lost in MPNST, was retained in all cases. In the control ERMS group, 5 of 7 (71%) showed RAS mutations, equally distributed among NRAS, KRAS, and HRAS genes. The expression profiling of MEM showed upregulation of skeletal muscle and neuronal genes, with no significant overlap with MPNST. Our results of common HRAS mutations and composite gene signature with RMS and neuronal/neuroblastic elements suggest a closer genetic link of MEM to RMS rather than to MPNST.

Background: Recurrent, metastatic mesenchymal myxoid tumors of the gynecologic tract present a management challenge as there is minimal evidence to guide systemic therapy. Such tumors also present a diagnostic dilemma, as myxoid features are observed in leiomyosarcomas, inflammatory myofibroblastic tumors (IMT), and mesenchymal myxoid tumors. Comprehensive genomic profiling was performed in the course of clinical care on a case of a recurrent, metastatic myxoid uterine malignancy (initially diagnosed as smooth muscle tumor of uncertain malignant potential (STUMP)), to guide identify targeted therapeutic options. To our knowledge, this case represents the first report of clinical response to targeted therapy in a tumor harboring a DCTN1-ALK fusion protein., Methods: Hybridization capture of 315 cancer-related genes plus introns from 28 genes often rearranged or altered in cancer was applied to >50 ng of DNA extracted from this sample and sequenced to high, uniform coverage. Therapy was given in the context of a phase I clinical trial ClinicalTrials.gov Identifier: ( NCT01548144 )., Results: Immunostains showed diffuse positivity for ALK1 expression and comprehensive genomic profiling identified an in frame DCTN1-ALK gene fusion. The diagnosis of STUMP was revised to that of an IMT with myxoid features. The patient was enrolled in a clinical trial and treated with an anaplastic lymphoma kinase (ALK) inhibitor (crizotinib/Xalkori®) and a multikinase VEGF inhibitor (pazopanib/Votrient®). The patient experienced an ongoing partial response (6+ months) by response evaluation criteria in solid tumors (RECIST) 1.1 criteria., Conclusions: For myxoid tumors of the gynecologic tract, comprehensive genomic profiling can identify clinical relevant genomic alterations that both direct treatment targeted therapy and help discriminate between similar diagnostic entities.

Uterine sarcomas and mixed epithelial-mesenchymal uterine tumors are a heterogeneous group of rare tumors for which there are very few diagnostic markers available. As aberrant microRNA (miRNA) expression patterns represent putative diagnostic cancer markers, we aimed to identify miRNA expression profiles of the major uterine sarcoma subtypes and mixed epithelial-mesenchymal tumors of the uterus. Eighty-eight miRNAs were assessed by quantitative RT-PCR in cancerous and non-cancerous tissue samples collected from 29 patients with endometrial sarcoma, leiomyosarcoma, and mixed epithelial-mesenchymal tumors. Tumor and control samples significantly (P < 0.05) differed in the expression of miR-23b, miR-1, let-7f, and let-7c in endometrial sarcomas, and miR-1, let-7c, miR-133b, let-7b, miR-143, let-7a, let-7d, let-7e, let-7g, miR-222, let-7i, and miR-214 in mixed epithelial-mesenchymal tumors. All the significantly changed miRNAs were down-regulated in the malignant tissues as compared to their normal counterparts. This may suggest their tumor suppressor role in these malignancies. No statistically significant changes in miRNA expression levels were found between leiomyosarcoma tumors and controls. The identified miRNAs warrant further studies as valuable candidate markers for the differential diagnosis of uterine sarcomas from benign uterine lesions and between uterine sarcoma subtypes.

Phosphaturic mesenchymal tumor of mixed connective tissue type is a rare, histologically distinctive mesenchymal neoplasm associated with tumor-induced osteomalacia resulting from production of the phosphaturic hormone fibroblast growth factor 23. Because of its rarity, specific genetic alterations that contribute to the pathogenesis of these tumors have yet to be elucidated. Herein, we report the abnormal karyotypes from 2 cases of confirmed phosphaturic mesenchymal tumor of mixed connective tissue type. G-banded analysis demonstrated the first tumor to have a karyotype of 46,Y,t(X;3;14)(q13;p25;q21)[15]/46XY[5], and the second tumor to have a karyotype of 46, XY,add(2)(q31),add(4)(q31.1)[2]/92,slx2[3]/46,sl,der(2)t(2;4)(q14.2;p14),der(4)t(2;4)(q14.2;p14),add(4)(q31.1)[10]/46,sdl,add(13)(q34)[4]/92,sdl2x2[1]. These represent what is, to our knowledge, the first examples of abnormal karyotypes obtained from phosphaturic mesenchymal tumor of mixed connective tissue type., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Ectomesenchymoma is a rare mesenchymal malignancy occurring mainly in the pediatric population. The hallmark diagnostic features are a combination of sarcoma, usually rhabdomyosarcoma (RMS) with admixed ganglion cells. The lesion arises either in soft tissues or the cranial cavity, and outcomes vary considerably. Current knowledge about the genetics and biology of ectomesenchymoma is extremely limited with only 4 published karyotypes, showing overlaps only in trisomies 2, 8, and 11. Here, we describe a case with genetic findings that, in conjunction with preexisting observations, offer some additional insights into the genetic aberrations of ectomesenchymoma., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Pleomorphic hyalinizing angiectatic tumor of soft parts is a recently recognized, low-grade mesenchymal neoplasm of uncertain lineage. It is characterized by clusters of ectatic, fibrin-lined, thin-walled vessels surrounded by pleomorphic but mitotically inert spindled cells with frequent intranuclear inclusions and a variable inflammatory component. Here, we report a case of recurrent pleomorphic hyalinizing angiectatic tumor in a 37-year-old white woman. Touch imprint cytologic analysis revealed oval and spindled cells with fine chromatin, occasional prominent intranuclear inclusions, and intracytoplasmic pigment. The histologic features of the cells constituting the bulk of tumor were those characteristic of a putative precursor lesion ("early pleomorphic hyalinizing angiectatic tumor") as well as another recently described entity known as hemosiderotic fibrohistiocytic lipomatous lesion. Cytogenetic analysis revealed 2 unbalanced translocations involving chromosomes 1 and 3 and chromosomes 1 and 10, with a karyotype of 45,XX,der(1)t(1;3)(p31;q12),-3,der(10)t(1;10)(p31;q25)[11]/46,XX[4], thus suggesting that this disease is neoplastic. The controversies in classification of these lesions are also discussed., (Copyright © 2012 Elsevier Inc. All rights reserved.)

Gastroblastoma is a rare gastric epitheliomesenchymal biphasic tumour composed of spindle and epithelial cells, reported by Miettinen et al in a series of three cases in 2009. All those cases arose in stomachs of young adults. Neither the epithelial nor the mesenchymal component displayed sufficient atypia to diagnose a carcinosarcoma or other malignancy. On immunohistochemistry, the epithelial component expressed cytokeratin, and the mesenchymal component was positive for vimentin and CD10. Miettinen et al designated these neoplasms as gastroblastomas based on their similarities with other childhood blastomas such as pleuropulmonary blastoma and nephroblastoma. This report describes a probable fourth case of this unique type of neoplasm. The present case arose in the gastric antrum of a 9-year-old boy. While similarities were evident with the other cases, there were some differences. The epithelial component was more predominant and showed more mature morphology. Immunohistochemically, the epithelial component showed immunolabelling for c-KIT and CD56. The mesenchymal component was only focally positive for CD10. Ultrastructually, desmosomes and microvilli were found supporting a truly epithelial lesion.

Phosphaturic mesenchymal tumors of the mixed connective tissue type (PMTMCT) are extremely rare, histologically distinctive neoplasms, which cause tumor-induced osteomalacia (TIO) in most cases through the elaboration of a phosphaturic hormone, fibroblast growth factor-23 (FGF23). Rarely, identical tumors without known TIO may be observed. We studied a large group of PMTMCT for expression of FGF23, using a novel reverse transcription polymerase chain reaction (RT-PCR) assay for FGF23 in formalin-fixed, paraffin-embedded tissues. Twenty-nine PMTMCT (17 with and 12 without TIO) and 23 non-PMTMCT (16 various mesenchymal tumors, including 5 chondromyxoid fibroma, 8 chondroblastoma, 1 hemangiopericytoma, 1 aneurysmal bone cyst, and 1 high grade sarcoma; 5 carcinomas; and 2 non-neoplastic tissues) were retrieved. Total RNA was extracted from formalin-fixed, paraffin-embedded sections for RT-PCR analysis. FGF23 was amplified using 3 sets of primers that spanned the intron/exon boundaries to amplify the 3 exons of FGF23 gene (140, 125, and 175 bp). The housekeeping gene phosphoglycerokinase (189 bp) was coamplified to check the RNA quality. Sixteen of 17 (94%) PMTMCT with TIO were FGF23-positive. Nine of 12 (75%) PMTMCT without TIO were FGF23-positive. Two chondromyxoid fibroma and 1 aneurysmal bone cyst were positive; all other non-PMTMCT were negative. We conclude that RT-PCR for FGF23 is a sensitive and specific means of confirming the diagnosis of PMTMCT both in patients with and without TIO. FGF23 gene expression was present in more than 90% of PMTMCT with known TIO, confirming the role of FGF23 in this syndrome. Rare FGF23-negative PMTMCT with known TIO likely express other phosphaturic hormones (eg, frizzled-related protein 4). Our finding of expression of FGF23 in 75% of histologically identical tumors without known TIO confirms the reproducibility of the diagnosis of PMTMCT, even in the absence of known phosphaturia.

Gastrointestinal stromal tumors (GISTs), generally KIT-positive and KIT/PDGFRA mutation-driven mesenchymal neoplasms, most commonly originate from the stomach or small intestine, but in rare examples they involve the omentum. In this study, we analyzed 95 GISTs surgically designated as the omental masses. These tumors occurred in 49 males and 46 females with a median age of 60 years (range: 27 to 88 y). They formed single (n=51) or multiple masses (n=39); 5 cases were equivocal in this respect. Of the single tumors, 21 had no evidence of gastrointestinal tract involvement, 25 were attached to stomach, and 3 were attached to small intestine. Clinicopathologic parameters and prognosis of the 2 former groups were similar. Single tumor cases showed a median mitotic count of 2/50 HPFs and median tumor size was 14 cm. Their histologic features were similar to gastric GISTs in 22 cases, and to small intestinal GISTs in 6 cases. These tumors were KIT positive 38/41, CD34 positive 20/33, 8 had PDGFRA mutations, and 6 had KIT exon 11 mutations. The median survival was 129 months (range: 0 to 397 mo) and 14 patients were alive at the end of follow-up. Multiple tumor cases showed median mitotic count of 14/50 HPFs and the main tumor median size was 16 cm. The histologic features were similar to small intestinal GISTs in 21 cases and to gastric GISTs in 7 cases; small intestinal attachment or history of a previous small intestinal GIST were noted in 5 cases, whereas no tumor was attached to stomach. The multiple GISTs were KIT positive 23/24, CD34 positive 7/21, and 5 had KIT exon 11 mutations, 3 had KIT exon 9 mutations, and 2 had PDGFRA mutations. The median survival was for 8 months and all patients died. Omental GISTs are clinicopathologically heterogenous. Patients with solitary tumors usually have gastric GIST-like morphology and a better prognosis than those with multiple tumors, whose tumor usually has small intestinal GIST-like histology. Omental GISTs unattached to gastrointestinal tract often resemble gastric GISTs suggesting that they may be gastric GISTs directly extending or parasitically attached into the omentum, whereas multiple omental GISTs more often resemble small intestinal GISTs suggesting that they may be metastatic or detached from this source. KIT positive Cajal cells were not found in normal omental tissues failing to support the presence of these ancestral cells for GIST in the omentum.

Purpose of Review: Desmoid tumors are associated with a variable and unpredictable clinical course. Surgery is the therapeutic mainstay, but there has been much discussion of late regarding its proper application. Little is known regarding the molecular determinates of desmoid tumor behavior. Some recent work has focused on the role of beta-catenin in desmoid tumor biology., Recent Findings: Given the variable clinical course of desmoid tumors, the interpretation of factors classically associated with recurrence such as microscopic status of margins appears more nuanced that previously thought. The application of multidisciplinary assessment with multimodality treatment, including surgery, radiation and systemic therapies may underlie these changes and now form the basis of care for this tumor. The precise CTNNB1 mutation present appears to be strongly predictive of recurrence after initial resection in one large, retrospective, multivariate analysis., Summary: Establishing the population benefiting most from various treatment modalities and combinations is critical for progress in this disease. Assessment and treatment of individual patients in a multidisciplinary setting is critical to achieve the most favorable outcome. Additional study of the molecular determinates of desmoid behavior is needed to guide therapeutic selection.

Gastrointestinal stromal tumors are the most common mesenchymal neoplasms of gastrointestinal tract often driven by oncogenic KIT exon 11 mutations. Although deletions and substitutions are most frequent KIT exon 11 mutations, duplications and insertions have been reported as well. In contrast to duplications, which cluster in 3'KIT exon 11, insertions affect 5'KIT, particularly codon 558. Clinicopathologic profile of gastrointestinal stromal tumors with insertions in codon 558 is not known. In this study, 17 gastrointestinal stromal tumors with codon 558 insertions are reported. Fifteen (88.2%) KIT codon 558 insertions consisted of 1694&#95;1695insTCC leading to Lys558delinsAsnPro. However, 2 variant mutants Lys558delinsAsnGln and Lys558delinsAsnAsn were also identified. Based on analysis of inserted and flanking sequences, the insertions contain inverted DNA sequences of the opposite strand. Therefore, these insertions may develop due to a DNA strand switch during replication by DNA polymerases and by the effects of several different DNA repair processes. Patient median age was 61 years, and male-to-female ratio was 1:1.8. gastrointestinal stromal tumors were diagnosed in stomach (n = 4), small intestine (n = 7), and rectum (n = 3). Three tumors were disseminated and primary location could not be established. Fourteen tumors had spindle cell morphology, and epithelioid cell features were seen in 2 intestinal and 1 disseminated gastrointestinal stromal tumor. Based on size and mitotic activity, 2 (50%) of 4 gastric and 3 (48.9%) of 7 small intestinal gastrointestinal stromal tumors had more than 50% risk of metastases according to previous studies of gastrointestinal stromal tumor prognosis. All 3 rectal gastrointestinal stromal tumors were malignant. Metastases were verified in 8 (66.7%) of 12 patients with known clinical and follow-up data. In summary, KIT codon 558 insertions are rare mutations accounting for less than 1% of all KIT mutants. Gastrointestinal stromal tumors with these mutations appear to have predilection to female patients and intestinal location. Moreover, KIT codon 558 insertions might indicate an increased risk of malignant behavior for gastric gastrointestinal stromal tumors.

Inflammatory fibroid polyps (IFPs) are mesenchymal tumours which arise in the submucosa and mucosa of the gastrointestinal tract. To date, the pathogenesis is unknown and IFPs are considered reactive and non-neoplastic lesions. Investigating a series of 23 IFPs, we made the observation that the tumours consistently express PDGFRA. To further elucidate the pathogenetic role of PDGFRA, we performed mutational analyses of exons 10, 12, 14, and 18. As IFPs are characterized by an inflammatory infiltrate rich in eosinophils, we used fluorescence in situ hybridization in a subset of tumours to investigate a possible FIP1L1-PDGFRA translocation which is known as the cause of hypereosinophilic syndrome (HES). Sixteen IFPs (70%) harboured activating mutations in exons 12 and 18, respectively: V561D (n = 1), R560SDelta561-567 (n = 1), Delta559-561D591H (n = 1), S566RDelta567-571 (n = 3), D842V (n = 7), D842I (n = 1), Delta842-845 (n = 1), and Delta845-848 (n = 1). These mutations equal pathogenic mutations detected in gastrointestinal stromal tumours previously. Activating mutations in exons 10 and 14 were not noted. None of the cases revealed the FIP1L1-PDGFRA translocation. Considering the remarkable number of activating mutations detected in our series, we conclude that the vast majority of IFPs harbour gain-of-function mutations in the PDGFRA gene. The presence of PDGFRA mutations questions the reactive nature of IFPs and raises the possibility of a neoplastic process.

Gastrointestinal stromal tumors (GISTs) are characterized by the presence of activating mutations affecting the c-Kit or the PDGFRA gene. Although these mutations are mutually exclusive, their proteins are coexpressed in many GISTs with various modulations of immunostaining depending on which gene is mutated. CD117 expression is currently considered a sensitive (although not entirely specific) marker of KIT activation, but there is no consensus concerning the reliability of PDGFRA antibody. Our database contains 236 molecularly analyzed GISTs, and we here describe the 180 cases that underwent KIT/PDGFRA immunophenotyping. By correlating the immunophenotype with the molecular status of the genes expected to be involved, we observed the coexpression of KIT and PDGFRA in the majority of the mutated c-Kit and wild-type c-Kit/PDGFRA GISTs, whereas the -/+ immunophenotype (0% vs. 48.6%) and PDGFRA dotlike immunostaining (P<0.005) segregated with the PDGFRA-mutated GISTs. Taking either the dotlike decoration (26 cases) or -/+ immunophenotype (5 cases) as hallmarks of PDGFRA mutation, the presence of a PDGFRA mutation was predicted in 31 (83.8%) of the 37 PDGFRA mutated GISTs. Our findings suggest that, when critically applied, the routine use of CD117/PDGFRA immunophenotyping is a useful diagnostic tool (especially in CD117-negative cases) as it correctly predicts the presence of PDGFRA mutations in most cases.

Aim: To assess the expression of CD137 and CD137L in human primary tumor tissues and their potential role in tumor immunity., Methods: Expression of CD137 and CD137L was assessed by immunohistochemistry in frozen sections of 12 human normal tissues, 15 benign tumors of epithelial or mesenchymal origin (adenoma and leiomyoma), and 36 malignant tumors of epithelial origin (squamous cell carcinoma and adenocarcinoma). The expression of CD137L on 9 human tumor cell lines (3 hepatocarcinoma, 2 lung carcinoma, 2 colon carcinoma, 1 lymphoma, and 1 leukemia) was detected by reverse transcription polymerase chain reaction. To analyze the role of CD137L expressed on tumor cells, we co-cultured tumor cells expressing CD137L with activated T lymphocytes expressing CD137 or with Chinese hamster ovary cells expressing CD137 and then detected by ELISA the levels of cytokines (IL-8, IFN-gamma) secreted by tumor cells or activated T cells., Results: The expression of CD137 and CD137L was observed only in human benign (2/15, 3/15) or malignant tumors (15/36, 21/36), but not in normal tissues (0/12, 0/12). CD137 was expressed on the vessel walls within tumor tissues, whereas CD137L was expressed on tumor cells. The expression of CD137 and CD137L was more common in malignant tumors, especially in moderate or low-differentiated tumors. Furthermore, CD137L expression found on tumor cell lines was functional because the ligation of CD137L on lung squamous carcinoma cells L78 with CD137 on T cells induced IFN-gamma production by T cells, and ligation of CD137L on hepatocarcinoma cells HepG2.2.15 with CD137 triggered tumor cells to produce IL-8., Conclusion: CD137 and CD137L are expressed in different human primary tumor tissues, suggesting that they may influence the progression of tumors.

The human herpes virus 8 (HHV-8)-encoded G protein-coupled chemokine receptor (vGPCR) has been implicated in the pathogenesis of Kaposi's sarcoma (KS), particularly because of its high constitutive signaling activity. Here, we used retroviral transduction to generate vGPCR-expressing 3T3 fibroblasts that are tumorigenic in nude mice, but as expected fail to induce tumors in their immunocompetent counterparts. However, tumor fragments obtained from nude mice grow progressively in immunocompetent BALB/c mice. Unexpectedly, vGPCR-expressing cells established from grafted tumor fragments gave rise to tumors in immunocompetent mice. These tumors exhibit a striking histological resemblance to KS including plump spindle cell morphology, a high degree of vascularization and brisk mitotic activity. High expression of vGPCR was confirmed in the cell lines and tumors using a newly developed vGPCR-specific monoclonal antibody. Finally, short interfering RNA directed at vGPCR abrogated or significantly delayed tumorigenesis in mice, demonstrating that the tumor development is specifically driven by vGPCR. This novel model for vGPCR-mediated oncogenesis will contribute to our understanding of the role of vGPCR in the pathogenesis of HHV-8 and may even be important in identifying critical molecular and epigenetic changes during tumor progression in vivo.

Gene microarray has been used to identify prognostic markers and genes of interest for therapeutic targets; a less common use is to show possible histogenetic relationships between rare tumor types and more common neoplasms. Intracranial malignant ectomesenchymoma (MEM) is a pediatric tumor postulated to arise from neural crest cells that contain divergent neuroectodermal and mesenchymal tissues, principally mature ganglion cells and rhabdomyosarcoma (RMS). We investigated a case of MEM by molecular, cytogenetic, and gene array analyses and compared results with our previously unpublished series of 51 pediatric tumors including conventional RMS, Ewing sarcoma (EWS), medulloblastoma (MED), atypical teratoid rhabdoid tumor (ATRT), and malignant peripheral nerve sheath tumor (MPNST); the latter is a sarcoma also with potential for divergent differentiation. Standard cytogenetic analyses and RT-PCR testing for the classic gene rearrangements seen in RMS [t(2;13)-PAX3/FKHR] and EWS ([t(11;22) & t(21;22)-EWS/FLI-1 & EWS/ERG), were used for characterization of the MEM, with gene expression microarray analyses on all tumor types. Gene rearrangement studies were negative in MEM. Gene expression microarray analyses showed tight clustering of the MEM with the MPNST (n = 2), but divergence from other pediatric tumors. MEM and MPNST both showed complex karyotypes, but without diagnostic translocations. Despite the presence of malignant skeletal muscle differentiation in the MEM, gene array testing showed no overlap with RMS, MED, or ATRT, but rather with MPNST. This suggests a common stem cell origin or embryonic gene recapitulation for these tumors and provides novel insights into their underlying biology.

Undifferentiated embryonal sarcoma of the liver is a highly malignant and aggressive tumor that occasionally arises within mesenchymal hamartoma of the liver (MHL), a benign tumor that typically occurs in young children. Undifferentiated embryonal sarcoma arising in MHL, as well as uncomplicated MHL, frequently harbor rearrangements of band 19q13.4, including the translocation t(11;19)(q13;q13.4). In this study we report the cloning and DNA sequence analysis of the translocation breakpoints in an undifferentiated embryonal sarcoma arising in MHL known to harbor t(11;19). In this case, the breakpoint at 11q13 occurred in the MALAT1 gene, also known as ALPHA. MALAT1 is rearranged in renal tumors harboring the t(6;11)(p21;q13) translocation, and noncoding MALAT1 transcripts are overexpressed in a number of human carcinomas. The breakpoint at 19q13.4 occurs at a locus we refer to as MHLB1, for Mesenchymal Hamartoma of the Liver Breakpoint 1. Although the MHLB1 locus does not contain a known gene, several human ESTs map to the region (a subset of which show homology to the nuclear RNA export factor (NXF) gene family), and the region is conserved between many mammalian species., ((c) 2007 Wiley-Liss, Inc.)

The protooncogene c-kit encoding transmembrane tyrosine kinase receptor protein plays an important role in the signal transduction pathway that regulates cellular growth and repair. Gene product KIT overexpression has been shown in a number of different neoplasms, particularly in mastocytosis and gastrointestinal stromal tumours (GIST). The morphologic similarity of uterine mesenchymal tumours and GIST, and the presence of KIT protein in normal uterine tissue, suggests that uterine sarcomas may have the same c-kit overexpression. The purpose of this study was to determine the overexpression of c-kit protein in uterine and ovarian sarcomas. Immunohistochemical staining using a polyclonal anti-c-kit antibody was performed on tissue blocks from 12 carsinosarcomas, 14 leiomyosarcomas, 8 endometrial stromal sarcomas, 2 adenosarcomas, 1 atypical leiomyoma, 1 leiomyoma with limited experience, and 10 leiomyomas. The slides were evaluated by a semiquantitative method. C-kit was positive in 10 of 12 (83%) carcinosarcomas, 10 of 14 (71%) leiomyosarcomas, 6 of 8 75(%) endometrial stromal sarcomas, 1 of 2 (50%) adenosarcomas, 1 leiomyoma with limited experience, and 1 of 10 (10%) leiomyomas. The uterine sarcomas express c-kit, like GISTs. It seems that KIT may have a significant role in the oncogenesis of mesenchymal tumours of the uterus and ovary.

Gastrointestinal (GI) stromal tumors (GISTs), the specific KIT- or PDFGRA-signaling driven mesenchymal tumors, are the most common mesenchymal tumors of the GI tract. This study analyzed 1091 tumors originally classified as smooth muscle tumors of the small intestine (including jejunum or ileum and excluding duodenum), and found that 906 (83%) of these were GISTs. The GIST patients had 55:45 male-to-female ratio with a median age of 59 years (range, 13-94 years). Only 0.6% of tumors occurred before the age of 21 years and 13.6% before the age of 40 years. The tumors varied from 0.3 to 40 cm (median, 7.0 cm) and most commonly presented with GI bleeding or acute abdomen; 18% were incidentally detected. Histologically, the tumors were relatively monotypic with spindle cell (86%), epithelioid (5%), or mixed patterns (9%). Skeinoid fibers were present in 44% of cases, and their presence was associated with a favorable course. Most epithelioid tumors were malignant, and this morphology sometimes emerged from less cellular and less mitotically active spindle cell tumors, suggesting that it represented a transformation. KIT was immunohistochemically detected in 98%, CD34 in 40%, smooth muscle actin in 34%, desmin in 0.2%, and S-100 protein in 14% of the tumors tested. Outcome was strongly dependent on tumor size and mitotic activity, with an overall 39% tumor-related mortality, twice that for gastric GISTs. Only <3% of tumors <5 cm and < or = 5 mitoses/50 HPF metastasized, whereas 86% of tumors >10 cm and >5 mitoses/50 HPF metastasized. In stark contrast to corresponding gastric tumors, tumors >10 cm with mitotic activity < or = 5/50 HPF and those < or = 5 cm with mitoses >5/50 HPF had a high metastatic rate (>50%); tumors >5 cm < or = 10 cm with low mitotic rate had a 24% metastatic rate. The median survival times of patients with low mitotic rate tumors who died of disease decreased by increasing tumor size. KIT exon 11 mutations were detected in 90 cases, exon 9 mutation in 17 cases, and exon 17 mutation in 1 case; the presence of mutation or mutation type was not prognostically significant. There were no PDGFRA exon 12 or 8 mutations. Systematic data on prognosis of small intestinal GISTs of various size and mitotic activity categories can be helpful in management and surveillance of patients with these tumors.

The present investigation examined the effect of bisphosphonates on six mesenchymal tumor cell lines and the mechanisms of inhibition of tumor cell proliferation. HT-1080, a fibrosarcoma cell line that exhibits increased Ras activity due to a mutation of the Ras gene, demonstrated significantly reduced tumor cell proliferation upon treatment with incadronate. The other cell lines, however, which lack mutation of the Ras gene, showed no influence upon treatment with incadronate. Autoradiography demonstrated no difference in the uptake of 3H-labelled incadronate between susceptible and unaffected cells. The anti-proliferation of HT-1080 was reversed by the addition of geranylgeranyl pyrophosphate. Etidronate exhibited no influence on all tested cell lines. On the basis of these data, we hypothesized that incadronate inhibits the mevalonate pathway and blocks oncogenic Ras signaling. In an effort to confirm this hypothesis, the influence of incadronate on an oncogenic Ras transfected BALB/3T3 cell line (Bhas 42) and a parental BALB/3T3 cell line were compared. The parental BALB/3T3 cells showed slight inhibition upon treatment with incadronate, however, the proliferation of Bhas 42 cells was significantly reduced. These results suggest that incadronate suppresses oncogenic Ras-activated mesenchymal tumors through the inhibition of Ras signaling pathways.

Familial gastrointestinal stromal tumor (GIST) is a rare autosomal dominant genetic disorder; thus far, only seven families have been reported with c-kit germline mutations. Presented herein is a case of multiple intestinal GIST in a 38-year-old man with a germline mutation of the c-kit gene. Operative specimens of the jejunal segment and multiple wedge resection specimens included approximately 30 masses, ranging in size from 1.0 to 6.0 cm. Microscopically, the tumors were composed of CD117-positive spindle/epitheloid cells with variable numbers of mitotic counts, a characteristic of GIST. The mitotic rate increased to more than 5/50 high-power fields. Interestingly, marked hypertrophy of the myenteric plexus with CD117-positive cells was identified in the intestinal segment. By polymerase chain reaction-single-strand conformation polymorphism analysis and direct DNA sequencing, a heterozygous c-kit missense mutation at nucleotide 1676 of codon 559 (T --> C, Val --> Ala), part of the juxtamembrane domain, was detected in the normal tissue. The same mutation was homozygous in the tumor samples. The present case is the first proven case of multiple GIST with a c-kit germline mutation in Korea and is distinguishable from other reported germ-line c-kit mutations because the same 1676 T --> C missense mutation occurs in the normal allele as well as the affected allele, although the significance of the identical mutations remains to be investigated.

Background: Mesenchymal neoplasia comprises a heterogeneous group of tumors with over 200 benign neoplasms and 100 sarcomas. Currently, tumors are classified using histologic and immunocytologic characteristics, with diagnostic error rates reported as high as 40% of cases. As a feasibility study, our goal was to generate a preliminary discriminatory gene list for selected mesenchymal tumors, including sarcomas. This technique may enable an eventual molecular classification schema based on expression profiles that can complement current clinical and pathologic diagnostic procedures in mesenchymal tumors., Methods: cDNA microarray analyses were preformed on connective tissue tumors obtained at time of surgical resection or biopsy. Messenger RNA (mRNA) from four general tumor classes was competitively hybridized against a human dermal fibroblast cell line comparator and the resulting gene expression profiles processed by ANOVA and linear discriminate analysis., Results: The tissue classification involved 18 patients with malignant peripheral nerve sheath tumors, giant cell containing tumors, benign spindle cell lesions, or Ewing's family of tumors. Lymph nodes from two patients served comparative purposes. Twenty-five differentially regulated genes considered most variable among the five tissue classes were identified. The tissues were segregated into five classes by linear discriminate analysis., Conclusions: Linear discriminate analysis of cDNA gene expression profiles partitioned mesenchymal tumor classes, even when constrained by limited sample sizes.

Background & Aims: Variability in the frequency of KIT mutations in gastrointestinal mesenchymal tumors has been reported in the literature, and their prognostic value remains uncertain. This retrospective multicenter study included 276 patients with gastrointestinal mesenchymal tumors., Methods: We detected c-kit and CD34 protein expression by immunohistochemistry. Mutations in exons 11 and 9 of KIT and exons 12 and 18 of PDGFR were detected by length analysis of polymerase chain reaction products and direct DNA sequencing., Results: Eighty-seven percent of the tumors analyzed were c-kit positive, with gastric tumors expressing CD34 more frequently than other tumors (86% vs. 52%; P < 0.001). KIT exon 11 mutations were detected in 90 of 179 (50.3%) of c-kit-positive and 12% of c-kit-negative tumors. These mutations showed variation in their length and location. Mutations were heterozygous in 94% of cases. Mutations were more frequent in CD34( +) tumors than in CD34( -) tumors ( P < 0.01), and 9% of tumors had a second mutation in exon 11. Mutations in exon 9 of KIT were present in 5.1% of the gastrointestinal stromal tumors, and mutations of the PDGFR were present in 11% of the KIT -nonmutated tumors. Patient's age, the primary location, size, necrosis, and mitotic counts of tumors were associated with metastases in c-kit-positive tumors. However, mitotic activity was the only independent factor identified in multivariate analysis ( P < 0.001). KIT mutations were slightly more frequent in metastatic than in nonmetastatic tumors (61% vs. 46%; P = 0.06). Deletions of codons 562-579 were more strongly associated with metastases than were deletions of codons 550-561 ( P = 0.0001)., Conclusions: Mutations in KIT or PDGFR were detected in 58.4% of the c-kit-positive and also in some c-kit-negative tumors.