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Ossifying fibroma of the craniofacial bones is a fibro-osseous lesion characterized by varied patterns of bone formation in a fibroblastic stroma. Ossifying fibroma is a putatively benign lesion with no reports of malignant transformation or metastasis. Differentiation from other fibro-osseous lesions can be challenging necessitating synthesis of clinical, radiological and pathological findings. The molecular pathogenesis of ossifying fibroma is poorly understood but recent studies have reported MDM2 gene amplification and chromosomal copy number changes in a subset of ossifying fibromas. MDM2 amplification in ossifying fibroma, if true, presents a diagnostic problem because this genetic event, at least among craniofacial fibro-osseous lesions, was previously considered specific for low-grade osteosarcoma. In the present study, we investigated the utility of MDM2 and CDK4 immunohistochemistry, and fluorescence in situ hybridization for MDM2 gene amplification, in the diagnosis of 44 craniofacial bone ossifying fibromas. Focal MDM2 and CDK4 nuclear immunoreactivity was found in 11 and 1 ossifying fibromas, respectively, but none demonstrated MDM2 amplification by fluorescence in situ hybridization. A single tumor displayed MDM2 amplification without nuclear immunoreactivity to either MDM2 or CDK4. Our data suggest that while focal MDM2 and CDK4 nuclear expression may be detected in a minority of ossifying fibromas, this expression does not correlate with MDM2 amplification. In addition, MDM2 amplification is extremely rare in ossifying fibroma so the detection of this genetic abnormality should continue to raise concern for osteosarcoma.

'Intracranial mesenchymal tumor, FET-CREB fusion-positive' occurs primarily in children and young adults and has previously been termed intracranial angiomatoid fibrous histiocytoma (AFH) or intracranial myxoid mesenchymal tumor (IMMT). Here we performed genome-wide DNA methylation array profiling of 20 primary intracranial mesenchymal tumors with FET-CREB fusion to further study their ontology. These tumors resolved into two distinct epigenetic subgroups that were both divergent from all other analyzed intracranial neoplasms and soft tissue sarcomas, including meningioma, clear cell sarcoma of soft tissue (CCS), and AFH of extracranial soft tissue. The first subgroup (Group A, 16 tumors) clustered nearest to but independent of solitary fibrous tumor and AFH of extracranial soft tissue, whereas the second epigenetic subgroup (Group B, 4 tumors) clustered nearest to but independent of CCS and also lacked expression of melanocytic markers (HMB45, Melan A, or MITF) characteristic of CCS. Group A tumors most often occurred in adolescence or early adulthood, arose throughout the neuroaxis, and contained mostly EWSR1-ATF1 and EWSR1-CREB1 fusions. Group B tumors arose most often in early childhood, were located along the cerebral convexities or spinal cord, and demonstrated an enrichment for tumors with CREM as the fusion partner (either EWSR1-CREM or FUS-CREM). Group A tumors more often demonstrated stellate/spindle cell morphology and hemangioma-like vasculature, whereas Group B tumors more often demonstrated round cell or epithelioid/rhabdoid morphology without hemangioma-like vasculature, although robust comparison of these clinical and histologic features requires future study. Patients with Group B tumors had inferior progression-free survival relative to Group A tumors (median 4.5 vs. 49 months, p = 0.001). Together, these findings confirm that intracranial AFH-like neoplasms and IMMT represent histologic variants of a single tumor type ('intracranial mesenchymal tumor, FET-CREB fusion-positive') that is distinct from meningioma and extracranial sarcomas. Additionally, epigenomic evaluation may provide important prognostic subtyping for this unique tumor entity.

The Warburg effect, aerobic glycolysis, is a hallmark feature of cancer cells grown in culture. However, the relative roles of glycolysis and respiratory metabolism in supporting in vivo tumor growth and processes such as tumor dissemination and metastatic growth remain poorly understood, particularly on a systems level. Using a CRISPRi mini-library enriched for mitochondrial ribosomal protein and respiratory chain genes in multiple human lung cancer cell lines, we analyzed in vivo metabolic requirements in xenograft tumors grown in distinct anatomic contexts. While knockdown of mitochondrial ribosomal protein and respiratory chain genes (mito-respiratory genes) has little impact on growth in vitro, tumor cells depend heavily on these genes when grown in vivo as either flank or primary orthotopic lung tumor xenografts. In contrast, respiratory function is comparatively dispensable for metastatic tumor growth. RNA-Seq and metabolomics analysis of tumor cells expressing individual sgRNAs against mito-respiratory genes indicate overexpression of glycolytic genes and increased sensitivity of glycolytic inhibition compared to control when grown in vitro, but when grown in vivo as primary tumors these cells down-regulate glycolytic mechanisms. These studies demonstrate that discrete perturbations of mitochondrial respiratory chain function impact in vivo tumor growth in a context-specific manner with differential impacts on primary and metastatic tumors.

BackgroundSoft-tissue sarcomas (STS) are a rare group of mesenchymal malignancies that account for approximately 1% of adult human cancer. Undifferentiated pleomorphic sarcoma (UPS) is one of the most common subtypes of adult STS. Clinical stratification of UPS patients has not evolved for decades and continues to rely on tumor-centric metrics including tumor size and depth. Our understanding of how the tumor microenvironment correlates to these clinicopathologic parameters remains limited.MethodsHere, we performed single-cell flow cytometric immune-based profiling of 15 freshly resected UPS tumors and integrated this analysis with clinical, histopathologic, and outcomes data using both a prospective and retrospective cohort of UPS patients.ResultsWe uncovered a correlation between physiologic and anatomic properties of UPS tumors and the composition of immune cells in the tumor microenvironment. Specifically, we identified an inverse correlation between tumor-infiltrating CD8 + T cells and UPS tumor size; and a positive correlation between tumor-infiltrating CD8 + T cells and overall survival. Moreover, we demonstrate an association between anatomical location (deep or superficial) and frequency of CD4 + PD1hi infiltrating T cells in UPS tumors.ConclusionsOur study provides an immune-based analysis of the tumor microenvironment in UPS patients and describes the different composition of tumor infiltrating lymphocytes based on size and tumor depth.

Intracranial mesenchymal tumors with FET-CREB fusions are a recently described group of neoplasms in children and young adults characterized by fusion of a FET family gene (usually EWSR1, but rarely FUS) to a CREB family transcription factor (ATF1, CREB1, or CREM), and have been variously termed intracranial angiomatoid fibrous histiocytoma or intracranial myxoid mesenchymal tumor. The clinical outcomes, histologic features, and genomic landscape are not well defined. Here, we studied 20 patients with intracranial mesenchymal tumors proven to harbor FET-CREB fusion by next-generation sequencing (NGS). The 16 female and four male patients had a median age of 14 years (range 4-70). Tumors were uniformly extra-axial or intraventricular and located at the cerebral convexities (n = 7), falx (2), lateral ventricles (4), tentorium (2), cerebellopontine angle (4), and spinal cord (1). NGS demonstrated that eight tumors harbored EWSR1-ATF1 fusion, seven had EWSR1-CREB1, four had EWSR1-CREM, and one had FUS-CREM. Tumors were uniformly well circumscribed and typically contrast enhancing with solid and cystic growth. Tumors with EWSR1-CREB1 fusions more often featured stellate/spindle cell morphology, mucin-rich stroma, and hemangioma-like vasculature compared to tumors with EWSR1-ATF1 fusions that most often featured sheets of epithelioid cells with mucin-poor collagenous stroma. These tumors demonstrated polyphenotypic immunoprofiles with frequent positivity for desmin, EMA, CD99, MUC4, and synaptophysin, but absence of SSTR2A, myogenin, and HMB45 expression. There was a propensity for local recurrence with a median progression-free survival of 12 months and a median overall survival of greater than 60 months, with three patients succumbing to disease (all with EWSR1-ATF1 fusions). In combination with prior case series, this study provides further insight into intracranial mesenchymal tumors with FET-CREB fusion, which represent a distinct group of CNS tumors encompassing both intracranial myxoid mesenchymal tumor and angiomatoid fibrous histiocytoma-like neoplasms.

Gnathic fibro-osseous lesions are a diverse group of disease processes which share overlapping microscopic features characterized by fibroblastic stroma with variable cellularity and a range of bone forming pathological processes leading to woven, sclerotic and cementum-like structures. Some of the lesions are unique to craniofacial location and a combination of clinical, radiological and pathological correlation is often necessary for diagnostic accuracy. Gnathic osteosarcomas are rare tumors with differences in age distribution and behavior as compared to osteosarcoma of long bones. This review will discuss the clinicopathological and radiological features of gnathic fibro-osseous lesions and osteosarcoma with updates on current genetics and molecular pathogenesis.

BackgroundMalignant peripheral nerve sheath tumor (MPNST) is an aggressive and poorly understood malignant neoplasm. Even in the setting of multimodal therapy, the clinical course of MPNST is frequently marked by metastatic conversion and poor overall prognosis, with optimal treatment paradigms for this rare tumor unknown.MethodsWe reviewed the medical records and histopathology of 54 consecutive patients who were treated at University of California San Francisco between 1990 and 2018.ResultsOur cohort consisted of 24 male and 30 female patients (median age 38 years). Fédération Nationale des Centres de Lutte Contre Le Cancer (FNCLCC) sarcoma grading criteria segregated patients into groups with differences in overall survival (OS) (P = .02). Increasing Ki-67 labeling index was associated with poor OS (hazard ratio [HR] 1.36 per 10%, P = .0002). Unsupervised hierarchical clustering-based immunohistochemical staining patterns identified 2 subgroups of tumors with differences in H3K27me3, Neurofibromin, S100, SOX10, p16, and EGFR immunoreactivity. In our cohort, cluster status was associated with improved locoregional failure-free rate (P = .004) in response to radiation.ConclusionsOur results lend support to the FNCLCC sarcoma grading criteria as a prognostic scheme for MPNST, although few cases of grade 1 were included. Further, we identify increased Ki-67 labeling as a strong predictor of poor OS from MPNST. Finally, we identify a subset of MPNSTs with a predictive immunohistochemical profile that has improved local control with adjuvant radiotherapy. These data provide insights into the grading and therapy for patients with MPNST, although further studies are needed for independent validation.

Magnetic resonance-guided focused ultrasound (MRgFUS) is a novel non-invasive ablation technique that uses focused sound energy to destroy focal tumors, primarily via heat deposition. It is widely used for palliation of pain from bone metastases and has also recently gained popularity as a technique for ablation of benign bone tumors and facet degenerative joint disease (rhizotomy). Clinically, in a subset of patients who have undergone MRgFUS of bone, a variety of treatment responses have been noted on follow-up imaging, including focal sclerosis within the target lesion or more exuberant proliferative changes associated with the periosteum. In this study, high resolution peripheral quantitative CT (HR-pQCT) was used to evaluate remodeling of bone following ablation in a swine model of MRgFUS and compared to samples from a control, non-treated femur. Within each treated femur, two lesions were created: a higher energy focused ultrasound dose was used for one lesion compared to a lower energy dose for the second lesion. Exuberant, extra-cortical bone formation was detected at the higher energy ablation zones, with volumes ranging from 340 mm3 to 1040 mm3. More subtle endosteal and cortical changes were detected in the lower energy ablation zones, however cortical thickness was significantly increased at these sites compared to control bone. For both high and low energy lesions, lower bone mineral density and tissue mineral density was noted in treated regions compared to control regions, consistent with the formation of newly mineralized tissue. Following HR-pQCT analysis, Fourier transform infrared (FTIR) spectroscopy was subsequently used to detect biochemical changes associated with remodeling of bone following MRgFUS, and compared to samples from the control, non-treated femur. Findings were compared with histopathologic examination following hematoxylin-eosin staining. FTIR analysis demonstrated lower mineral/phosphate ratio and increased crystallinity compared to the control samples (p = 0.013). Histopathologic review demonstrated associated areas of endosteal inflammation, scarring, fat necrosis, and new extra-cortical bone formation associated with the ablations. Overall, these findings provide novel characterization of new bone formation following MRgFUS ablation.

In April 2024, the Food and Drug Administration provided accelerated approval for trastuzumab deruxtecan for adult patients with advanced solid tumors which have positive immunochemical staining for HER2 expression, including sarcomas. There should be ample consideration prior to utilization of trastuzumab deruxtecan for patients with sarcomas, as HER2 targeted therapy has been ineffective in certain subtypes. [ABSTRACT FROM AUTHOR]

Cutibacterium (formerly Propionibacterium) acnes13, 16 is a slow growing, gram-positive bacteria that is naturally found in higher concentrations as skin flora on the chest and back, as well as in other areas with greater numbers of hair follicles.25, 37 Most of the reported cases of C. acnes shoulder girdle infection follow arthroplasty surgery,18, 20, 26, 27, 32, 35 which then often requires debridement, administration of intravenous antibiotics, and surgical revision of the implanted device.12, 15, 21, 28-30 In a recent study, 56% of 193 shoulder revisions had a positive culture, 70% of which grew C. acnes.30 Despite the relatively common presumed association of C. acnes humeral osteomyelitis with prosthetic infection, infection of the scapula or clavicle secondary to C. acnes is rare.4, 23, 36 Osteomyelitis of the clavicle involving any organism is also an uncommon event that can arise spontaneously via presumed hematogenous spread, or secondary to open fractures or internal fixation.6, 33 The most commonly found organism in clavicular osteomyelitis is Staphylococcus aureus.9 We here report two cases of clavicular infection secondary to C. acnes that were not associated with implants.

BackgroundDespite numerous discoveries regarding the molecular genesis and progression of primary cancers, the biology of metastasis remains poorly understood. Compared to very large numbers of circulating tumor cells that are now known to accompany nearly all cancers, a relatively limited number of lesions actually develop in most patients with metastases. We hypothesized that phenotypic changes driven by differential gene expression in a finite subpopulation of tumor cells render those cells capable of metastasis and sought to identify key pathways through analysis of gene expression in primary and metastatic lesions from the same patients.MethodsWe compared whole-genome expression in 4 matched samples of primary and metastatic sarcoma, then evaluated candidate genes with differential expression via quantitative PCR in 30 additional matched sets, tumor tissue immunostaining, siRNA loss-of-function in a sarcoma cell migration assay, and clinical correlation with overall and disease-free survival after metastasectomy.ResultsComparison of microarray signals identified differential expression of cell adhesion genes, including upregulation of KRT7 and MUC1 in metastases; KRT7 and MUC1 upregulation was confirmed in 22 (73%) and 20 (67%) matched sets of metastatic/primary tumors, respectively. Silencing of KRT7 and MUC1 via targeted siRNAs suppressed sarcoma cell migration in vitro, and a significant correlation (two-sided) was observed between both KRT7 and MUC1 expression in metastases and overall patient survival.ConclusionKRT7 and MUC1 may play a significant role in enabling sarcoma metastasis, and they may therefore be important prognostic biomarkers as well as potential targets for therapeutic prevention of metastasis.

Mesenchymal round cell tumors are a diverse group of neoplasms defined by primitive, often high-grade cytomorphology. The most common molecular alterations detected in these tumors are gene rearrangements involving EWSR1 to one of many fusion partners. Rare EWSR1-NFATC2 gene rearrangements, corresponding to a t(20;22) gene translocation, have been described in mesenchymal tumors with clear round cell morphology and a predilection for the skeleton. We present a case of a tumor harboring the EWSR1-NFATC2 gene fusion arising in the subcutaneous tissue of a young woman. The tumor exhibited corded and trabecular architecture of epithelioid cells within abundant myxoid and fibrous stroma. The cells showed strong immunoreactivity for NKX2.2, variable CD99, keratin, and epithelial membrane antigen, but were negative for S100 and myoepithelial markers. Importantly, similar to previously reported cases, the clinical course was more indolent than that of Ewing sarcoma. This case highlights the distinctive clinicopathological characteristics of EWSR1-NFATC2 gene fusion-associated neoplasms that distinguish them from Ewing sarcoma.

Perineal nodular induration (PNI), or biker's nodule, is a rare, bothersome, pseudotumour. Herein, we describe the surgical technique used to treat a healthy cyclist who developed an enlarging PNI for five years that grew into a perineal mass. The mass prevented him from cycling due to worsening discomfort and heaviness. The PNI-associated mass was successfully removed by wide surgical excision and a local advancement flap. Subsequently, the patient resumed cycling. Histopathology report demonstrated a benign lesion with abundant ropy collagen with native smooth muscle, vessels, and rare fibroblast-like spindle cells. With the increasing popularity of cycling, PNI may become more common, and health providers should be aware of this rare entity and how it can be safely removed.

Purpose: Second malignant neoplasms (SMNs) are severe late complications that occur in pediatric cancer survivors exposed to radiotherapy and other genotoxic treatments. To characterize the mutational landscape of treatment-induced sarcomas and to identify candidate SMN-predisposing variants, we analyzed germline and SMN samples from pediatric cancer survivors.Experimental Design: We performed whole-exome sequencing (WES) and RNA sequencing on radiation-induced sarcomas arising from two pediatric cancer survivors. To assess the frequency of germline TP53 variants in SMNs, Sanger sequencing was performed to analyze germline TP53 in 37 pediatric cancer survivors from the Childhood Cancer Survivor Study (CCSS) without any history of a familial cancer predisposition syndrome but known to have developed SMNs.Results: WES revealed TP53 mutations involving p53's DNA-binding domain in both index cases, one of which was also present in the germline. The germline and somatic TP53-mutant variants were enriched in the transcriptomes for both sarcomas. Analysis of TP53-coding exons in germline specimens from the CCSS survivor cohort identified a G215C variant encoding an R72P amino acid substitution in 6 patients and a synonymous SNP A639G in 4 others, resulting in 10 of 37 evaluable patients (27%) harboring a germline TP53 variant.Conclusions: Currently, germline TP53 is not routinely assessed in patients with pediatric cancer. These data support the concept that identifying germline TP53 variants at the time a primary cancer is diagnosed may identify patients at high risk for SMN development, who could benefit from modified therapeutic strategies and/or intensive posttreatment monitoring. Clin Cancer Res; 23(7); 1852-61. ©2016 AACR.

Aneurysmal bone cysts are uncommon primary bone tumors typically regarded as histologically and clinically benign. Malignant transformation of these lesions occurs almost exclusively in the context of prior radiation exposure. However, 4 cases of an osteosarcoma developing without prior radiation exposure have been reported. In this article, we report a fifth case of degeneration of an aneurysmal bone cyst to a fibroblastic osteosarcoma. In addition to reviewing the earlier cases, we describe the radiologic, pathologic, and immunohistochemical basis of this diagnosis.

Multiple hereditary exostoses is an autosomal dominant condition characterized by numerous benign osteochondromas. Complications are rare and can include deformity, growth abnormality, fracture, adventitial bursa formation, local mass effect on a nerve, malignant degeneration, and vascular complications including stenosis, occlusion, arteriovenous fistula, and pseudoaneurysm. We present a case of multiple hereditary exostoses leading to a deep femoral artery pseudoaneurysm in the proximal medial thigh with subsequent rupture and hematoma, masquerading as tumor.

BackgroundHead and neck cancer is often managed with a combination of surgery, radiation therapy, and chemotherapy, and skin toxicity is not uncommon. Xanthogranuloma is a pathological finding resulting from an inflammatory reaction that has not been previously reported following head and neck radiation therapy.Case presentationA patient with squamous cell carcinoma of the oropharynx, treated with definitive chemoradiation and hyperthermia, presented at eight-month follow-up with an in-field cutaneous lesion in the low neck, initially concerning for recurrent tumor. Biopsy showed xanthogranuloma and the patient underwent complete resection with congruent surgical pathology. The patient remained free of malignancy but continued to experience wound healing difficulties at the resection site which resolved with specialized wound care and hyperbaric oxygen.ConclusionsSkin toxicity is not uncommon in patients with head and neck cancer treated with radiation therapy. Awareness of unusual pathologic sequelae, such as xanthogranuloma, is needed to provide patient counseling while continuing appropriate surveillance for recurrent malignancy.

Cellular schwannoma is an uncommon, but well-recognized, benign peripheral nerve sheath tumor, which can be misdiagnosed as malignant peripheral nerve sheath tumor. To develop consensus diagnostic criteria for cellular schwannoma, we reviewed 115 malignant peripheral nerve sheath tumor and 26 cellular schwannoma cases from two institutions. Clinical data were retrieved from the electronic medical records, and morphologic features, maximal mitotic counts, Ki67 labeling indices, and immunohistochemical profiles (SOX10, SOX2, p75NTR, p16, p53, EGFR, and neurofibromin) were assessed. Several features distinguish cellular schwannoma from malignant peripheral nerve sheath tumor. First, in contrast to patients with malignant peripheral nerve sheath tumor, no metastases or disease-specific deaths were found in patients with cellular schwannoma. More specifically, 5-year progression-free survival rates were 100 and 18%, and 5-year disease-specific survival rates were 100 and 32% for cellular schwannoma and malignant peripheral nerve sheath tumor, respectively. Second, the presence of Schwannian whorls, a peritumoral capsule, subcapsular lymphocytes, macrophage-rich infiltrates, and the absence of fascicles favored the diagnosis of cellular schwannoma, while the presence of perivascular hypercellularity, tumor herniation into vascular lumens, and necrosis favor malignant peripheral nerve sheath tumor. Third, complete loss of SOX10, neurofibromin or p16 expression, or the presence of EGFR immunoreactivity was specific for malignant peripheral nerve sheath tumor (P

PurposeTo serially monitor bone remodeling in the swine femur after magnetic resonance (MR) imaging-guided high-intensity focused ultrasound (HIFU) ablation with MR imaging, computed tomography (CT), sodium fluorine 18 (Na(18)F)-positron emission tomography (PET), and histopathologic examination, as a function of sonication energy.Materials and methodsExperimental procedures received approval from the local institutional animal care and use committee. MR imaging-guided HIFU was used to create distal and proximal ablations in the right femurs of eight pigs. The energy used at the distal target was higher (mean, 419 J; range, 390-440 J) than that used at the proximal target (mean, 324 J; range, 300-360 J). Imaging was performed before and after ablation with 3.0-T MR imaging and 64-section CT. Animals were reevaluated at 3 and 6 weeks with MR imaging (n = 8), CT (n = 8), Na(18)F-PET (n = 4), and histopathologic examination (n = 4). Three-dimensional ablation lengths were measured on contrast material-enhanced MR images, and bone remodeling in the cortex was measured on CT images.ResultsAblation sizes at MR imaging 3 and 6 weeks after MR imaging-guided HIFU ablation were similar between proximal (low-energy) and distal (high-energy) lesions (average, 8.7 × 21.9 × 16.4 mm). However, distal ablation lesions (n = 8) demonstrated evidence of subperiosteal new bone formation at CT, with a subtle focus of new ossification at 3 weeks and a larger focus of ossification at 6 weeks. New bone formation was associated with increased uptake at Na(18)F-PET in three of four animals; this was confirmed at histopathologic examination in four of four animals.ConclusionMR imaging-guided HIFU ablation of bone may result in progressive remodeling, with both subcortical necrosis and subperiosteal new bone formation. This may be related to the use of high energies. MR imaging, CT, and PET are suitable noninvasive techniques to monitor bone remodeling after MR imaging-guided HIFU ablation.

We describe a 16-year-old boy with rhabdomyosarcoma, consistent with embryonal subtype, of the lower extremity who received systemic neoadjuvant chemotherapy and subsequent excision. Microscopic sections of the postchemotherapy excision demonstrated diffuse, prominent, and immature adipocyte-like differentiation, in addition to skeletal muscle differentiation. Adipocyte-like differentiation was confirmed by a combination of positive Oil Red O and adipophilin immunohistochemical staining. To our knowledge, this represents the first report of an unusual phenomenon of differentiation of a soft tissue rhabdomyosarcoma into adipocyte-like cells after chemotherapy.

Targeted therapies are increasingly being evaluated for patients with Ewing sarcoma (EWS). Optimal strategies for quantifying key signaling proteins in EWS remain unclear. We sought to quantify tumor expression of signaling pathway proteins in EWS using 3 methodologies. A total of 46 blocks of formalin-fixed paraffin-embedded tissue were obtained from 40 patients with EWS. Tumor was evaluated for the expression of proteins in the insulin-like growth factor type 1 receptor (IGF-1R), epithelial growth factor receptor (EGFR), and mTOR pathways using standard immunohistochemical analysis (IHC), automated quantitative analysis (AQUA) immunohistochemical analysis, and mass spectrometry quantification. The mean age at diagnosis was 14 years (range, 1 to 49 y). About 67.5% were male and 57.5% had localized disease. Samples displayed a wide range of expression by AQUA: mean (range) IGF-1R=10,702 (393 to 14,424); EGFR=2750 (672 to 9798); and phosphatase and tensin homolog (PTEN)=2250 (251 to 6557). Mean IGF-1R expression by AQUA did not differ between standard IHC expression categories (low IHC=11,255; medium IHC=11,070; high IHC=11,023; P=0.98). Mean PTEN expression by AQUA was higher in the medium and high IHC categories (low IHC=1229; medium IHC=2715; high IHC=2940; P=0.064). Only 2 samples expressed EGFR by standard IHC. Mass spectrometry trended toward correlation with standard IHC but did not yield interpretable results in the majority of samples. This study demonstrates that the relative quantification of signaling protein expression in EWS is dependent on the methodology used. Optimization and validation of these tools are necessary before clinical application for risk stratification of patients or measurement of biomarker expression.

The Ewing sarcoma family of tumors (EFT) is a group of highly malignant small round blue cell tumors occurring in children and young adults. We report here the largest genomic survey to date of 101 EFT (65 tumors and 36 cell lines). Using a combination of whole genome sequencing and targeted sequencing approaches, we discover that EFT has a very low mutational burden (0.15 mutations/Mb) but frequent deleterious mutations in the cohesin complex subunit STAG2 (21.5% tumors, 44.4% cell lines), homozygous deletion of CDKN2A (13.8% and 50%) and mutations of TP53 (6.2% and 71.9%). We additionally note an increased prevalence of the BRCA2 K3326X polymorphism in EFT patient samples (7.3%) compared to population data (OR 7.1, p = 0.006). Using whole transcriptome sequencing, we find that 11% of tumors pathologically diagnosed as EFT lack a typical EWSR1 fusion oncogene and that these tumors do not have a characteristic Ewing sarcoma gene expression signature. We identify samples harboring novel fusion genes including FUS-NCATc2 and CIC-FOXO4 that may represent distinct small round blue cell tumor variants. In an independent EFT tissue microarray cohort, we show that STAG2 loss as detected by immunohistochemistry may be associated with more advanced disease (p = 0.15) and a modest decrease in overall survival (p = 0.10). These results significantly advance our understanding of the genomic and molecular underpinnings of Ewing sarcoma and provide a foundation towards further efforts to improve diagnosis, prognosis, and precision therapeutics testing.

Precise regulation of bone resorption is critical for skeletal homeostasis. We report a 32-year-old man with a panostotic expansile bone disease and a massive hemorrhagic mandibular tumor. Originally from Mexico, he was deaf at birth and became bow-legged during childhood. There was no family history of skeletal disease. Puberty occurred normally, but during adolescence he experienced difficulty straightening his limbs, sustained multiple fractures, and developed a bony tumor on his chin. By age 18 years, all limbs were misshapen. The mandibular mass grew and protruded from the oral cavity, extending to the level of the lower ribs. Other bony defects included a similar maxillary mass and serpentine limbs. Upon referral at age 27 years, biochemical studies showed serum alkaline phosphatase of 1760 U/L (Nl: 29-111) and other elevated bone turnover markers. Radiography of the limbs showed medullary expansion and cortical thinning with severe bowing. Although the jaw tumors were initially deemed inoperable, mandibular mass excision and staged partial maxillectomy were eventually performed. Tumor histopathology showed curvilinear trabeculae of woven bone on a background of hypocellular fibrous tissue. Fibrous dysplasia of bone was suspected, but there was no mutation in codon 201 of GNAS in samples from blood or tumor. His clinical and radiographic findings, elevated serum markers, and disorganized bone morphology suggested amplified receptor activator of NF-κB (RANK) signaling, even though his disorder differed from conditions with known constitutive activation of RANK signaling (eg, familial expansile osteolysis). We found a unique 12-base pair duplication in the signal peptide of TNFRSF11A, the gene that encodes RANK. No exon or splice site mutations were found in the genes encoding RANK ligand or osteoprotegerin. Alendronate followed by pamidronate therapies substantially decreased his serum alkaline phosphatase activity. This unique patient expands the phenotypes and genetic basis of the mendelian disorders of RANK signaling activation.

Second malignant neoplasms (SMN) are therapy-induced malignancies and a growing problem in cancer survivors, particularly survivors of childhood cancers. The lack of experimental models of SMNs has limited understanding of their pathogenesis. It is currently not possible to predict or prevent this devastating late complication. Individuals with neurofibromatosis I (NF1) are at increased risk of developing therapy-induced cancers for unclear reasons. To model SMNs, we replicated clinical radiotherapy and delivered fractionated abdominal irradiation to Nf1(+/-) and wild-type mice. Similar to irradiated cancer survivors, irradiated wild-type and Nf1(+/-) mice developed diverse in-field malignancies. In Nf1(+/-) mice, fractionated irradiation promoted both classical NF1-associated malignancies and malignancies unassociated with the NF1 syndrome but typical of SMNs. Nf1 heterozygosity potentiated the mutagenic effects of irradiation, as evidenced by the significantly reduced survival after irradiation and tumor development that was often characterized by synchronous primary tumors. Interestingly, diverse radiation-induced tumors arising in wild-type and Nf1(+/-) mice shared a genetic signature characterized by monoallelic loss of Nf1 and the adjacent Trp53 allele. These findings implicate Nf1 loss as mediating tumorigenesis in a broad range of cell types and organs extending beyond the classical NF1 tumor histologies. Examining clinical SMN samples, we found LOH of NF1 in SMNs from non-NF1 patients. Nf1 heterozygosity confers broad susceptibility to genotoxin-induced tumorigenesis, and this paradigm serves as an experimental platform for future studies of SMNs.

Osteoid osteoma occurs most commonly in children, adolescents, and young adults between the ages of 5 and 30 years. In the preschool age group, it is quite uncommon, accounting for only 3-8% of all osteoid osteoma cases. We report a case of osteoid osteoma in a 7-month-old infant, who presented with decreased use of the right lower extremity due to pain. Magnetic resonance imaging (MRI) showed an atypical appearance. A biopsy of the lesion, with histopathological examination, confirmed the diagnosis of osteoid osteoma. Radiofrequency ablation (RFA) of the nidus under computed tomography (CT) guidance was performed. The patient developed a recurrence after 3 months, which was treated with a second RFA. On subsequent follow-up, the infant did not show signs of pain after 1 month. In summary, this case report shows that osteoid osteoma can present in early infancy and can be successfully treated with RFA at this age, however, recurrence after the procedure can occur and close follow-up is recommended.