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Lipoleiomyomas are rare variants of uterine leiomyomas rarely studied in the literature. We retrospectively studied 20 cases of uterine lipoleiomyomas showing that these lesions represent 0.7 % of all uterine leiomyomas diagnosed histologically. The patients did not experience any recurrence, and the tumors showed no morphological criteria of malignancy. They did not show significant p16, p53 or MiB1 expression. They showed diffuse and strong expression or estrogen and progesterone receptors by the smooth muscle component but without accompanying expression by the adipocytic component in one third of the cases. Androgen receptors were rarely expressed. They expressed in their majority HMGA2 in both components, while RB1 was usually not found. Fumarate hydratase (FH) is expressed by lipoleiomyomas, while they are negative for HMB45. In conclusion, uterine lipoleiomyomas are rare, benign tumors, characterized by HMGA2 expression, while they show no elements suspicious of malignancy, PEComas or FH deficiency. The role of RB1 in these tumors should be further explored., Competing Interests: Declaration of Competing Interest The authors have no conflict of interest to disclose., (Copyright © 2024 The Authors. Published by Elsevier GmbH.. All rights reserved.)

In arteries and arterioles, a chronic increase in blood pressure raises wall tension. This continuous biomechanical strain causes a change in gene expression in vascular smooth muscle cells (VSMCs) that may lead to pathological changes. Here we have characterised the functional properties of lipoma-preferred partner (LPP), a Lin11-Isl1-Mec3 (LIM)-domain protein, which is most closely related to the mechanotransducer zyxin but selectively expressed by smooth muscle cells, including VSMCs in adult mice. VSMCs isolated from the aorta of LPP knockout (LPP-KO) mice displayed a higher rate of proliferation than their wildtype (WT) counterparts, and when cultured as three-dimensional spheroids, they revealed a higher expression of the proliferation marker Ki 67 and showed greater invasion into a collagen gel. Accordingly, the gelatinase activity was increased in LPP-KO but not WT spheroids. The LPP-KO spheroids adhering to the collagen gel responded with decreased contraction to potassium chloride. The relaxation response to caffeine and norepinephrine was also smaller in the LPP-KO spheroids than in their WT counterparts. The overexpression of zyxin in LPP-KO VSMCs resulted in a reversal to a more quiescent differentiated phenotype. In native VSMCs, i.e., in isolated perfused segments of the mesenteric artery (MA), the contractile responses of LPP-KO segments to potassium chloride, phenylephrine or endothelin-1 did not vary from those in isolated perfused WT segments. In contrast, the myogenic response of LPP-KO MA segments was significantly attenuated while zyxin-deficient MA segments displayed a normal myogenic response. We propose that LPP, which we found to be expressed solely in the medial layer of different arteries from adult mice, may play an important role in controlling the quiescent contractile phenotype of VSMCs.

Lipomas are slow growing benign fat tumors that develop in soft tissues of the mesoderm. Thus, the specific (dys-)function of mesenchymal stem cells (MSCs) has been suggested in the development of lipomas, but details of the tumor pathogenesis remain unclear. Existing studies comparing stem cells from native adipose (adipose stem cells [ASCs]) and lipomatous tissues (LSCs) have reported contradicting findings. However, harvesting ASCs and LSCs from different individuals might have influenced proper comparison. Therefore, we aimed to characterize donor-matched ASCs and LSCs to investigate metabolic activity, proliferation, capability for tri-linear differentiation (chondrogenesis, adipogenesis, osteogenesis), and the secretome of mature adipocytes and lipomacytes. Both stem cell types did not differ in metabolic activity, but ASCs demonstrated stronger proliferation than LSCs. While there was no difference in proteoglycan accumulation during chondrogenic differentiation, adipogenesis was higher in ASCs, with more lipid vacuole formation. Conversely, LSCs showed increased osteogenesis by higher calcium deposition. Lipomacytes showed stronger secretory activity and released higher levels of certain adipokines. Our findings indicated that LSCs possessed important characteristics of MSCs, including ASCs. However, LSCs' low proliferation and adipogenic differentiation behavior did not appear to account for enhanced tissue proliferation, but the secretome of lipomacytes could contribute to lipomatous neoplasm., (© 2022 The Authors. Cell Biochemistry and Function published by John Wiley & Sons Ltd.)

Purpose: To evaluate the diagnostic capability of radiomics in distinguishing lipoma and Atypic Lipomatous Tumors/Well-Differentiated Liposarcomas (ALT/WDL) with Magnetic Resonance Imaging (MRI)., Materials and Methods: Patients with a histopathologic diagnosis of lipoma (n = 45) and ALT/WDL (n = 20), who had undergone pre-surgery or pre-biopsy MRI, were enrolled. The MDM2 amplification was accepted as gold-standard test. The T1-weighted turbo spin echo images were used for radiomics analysis. Utility of a predefined standardized imaging protocol and a single type of 1.5 T scanner were sought as inclusion criteria. Radiomics parameters that show a certain level of reproducibility were included in the study and supplied to Support Vector Machine (SVM) as a machine learning method., Results: No significant difference was found in terms of gender, location and age between the lipoma and ALT/WDL groups. Sixty-five parameters were accepted as reproducible. Fifty-seven parameters were able to distinguish the two groups significantly (AUC range 0.564-0.902). Diagnostic performance of the SVM was one of the highest among literature findings: sensitivity = 96.8% (95% CI 94.03-98.39%), specificity = 93.72% (95% CI 86.36-97.73%) and AUC = 0.987 (95% CI 0.972-0.999)., Conclusion: Although radiomics has been proven to be useful in previous literature regarding discrimination of lipomas and ALT/WDLs, we found that its accuracy could further be improved with utility of standardized hardware, imaging protocols and incorporation of machine learning methods., (© 2022. The Author(s) under exclusive licence to Japan Radiological Society.)

Small integral membrane protein 10 like 1 (SMIM10L1) was identified by RNA sequencing as the most significantly downregulated gene in Phosphatase and Tensin Homologue (PTEN) knockdown adipose progenitor cells (APCs). PTEN is a tumor suppressor that antagonizes the growth promoting Phosphoinositide 3-kinase (PI3K)/AKT/mechanistic Target of Rapamycin (mTOR) cascade. Diseases caused by germline pathogenic variants in PTEN are summarized as PTEN Hamartoma Tumor Syndrome (PHTS). This overgrowth syndrome is associated with lipoma formation, especially in pediatric patients. The mechanisms underlying this adipose tissue dysfunction remain elusive. We observed that SMIM10L1 downregulation in APCs led to an enhanced adipocyte differentiation in two- and three-dimensional cell culture and increased expression of adipogenesis markers. Furthermore, SMIM10L1 knockdown cells showed a decreased expression of PTEN, pointing to a mutual crosstalk between PTEN and SMIM10L1. In line with these observations, SMIM10L1 knockdown cells showed increased activation of PI3K/AKT/mTOR signaling and concomitantly increased expression of the adipogenic transcription factor SREBP1. We computationally predicted an α-helical structure and membrane association of SMIM10L1. These results support a specific role for SMIM10L1 in regulating adipogenesis, potentially by increasing PI3K/AKT/mTOR signaling, which might be conducive to lipoma formation in pediatric patients with PHTS., Competing Interests: Declaration of competing interest The authors declare no conflicts of interest. The funder had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript; or in the decision to publish the article., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

Aims: Amplification of the murine double minute-2 (MDM2) gene, which is usually detected with fluorescence in-situ hybridisation (FISH), is the key driving event for atypical lipomatous tumours (ALTs)/well-differentiated liposarcomas (WDLs). We sought to determine the concordance between the histopathological findings and MDM2 FISH in the diagnosis of ALT/WDL, and to identify the histological features of MDM2-amplified tumours lacking classic atypia., Methods and Results: We performed a retrospective analysis of all mature lipomatous lesions subjected to MDM2 FISH analysis at our institution. MDM2 FISH analysis was performed on 439 mature lipomatous lesions: 364 (82.9%) were negative and 75 (17%) were positive. In 17 of 75 (22.6%) ALTs/WDLs, cytological atypia was not identified on initial histological assessment, thus favouring lipoma. On review, these cases shared common histological features, consisting of a very low number of relatively small stromal cells within the tumour lobules, with mildly coarse chromatin and oval nuclei, admixed with unremarkable adipocytes in a tumour background devoid of fibroconnective septa, areas of fibrosis, or blood vessels. These cells matched the cells in which FISH showed MDM2 amplification. In contrast, 13 cases (3.5%) regarded as suspicious for ALT/WDL on the basis of histology lacked MDM2 amplification and were reclassified following the FISH findings., Conclusions: We conclude that a subset of lipoma-like ALTs/WDLs are not associated with any of the features typically described in ALT/WDL. Our study also showed that tumours >100 mm are more likely to be ALT/WDL; however, a history of recurrence or concerning clinical/radiological features was not significantly associated with classification as ALT/WDL., (© 2021 John Wiley & Sons Ltd.)

The tumor suppressor phosphatase and tensin homolog (PTEN) negatively regulates the insulin signaling pathway. Germline PTEN pathogenic variants cause PTEN hamartoma tumor syndrome (PHTS), associated with lipoma development in children. Adipose progenitor cells (APCs) lose their capacity to differentiate into adipocytes during continuous culture, whereas APCs from lipomas of patients with PHTS retain their adipogenic potential over a prolonged period. It remains unclear which mechanisms trigger this aberrant adipose tissue growth. To investigate the role of PTEN in adipose tissue development, we performed functional assays and RNA-Seq of control and PTEN knockdown APCs. Reduction of PTEN levels using siRNA or CRISPR led to enhanced proliferation and differentiation of APCs. Forkhead box protein O1 (FOXO1) transcriptional activity is known to be regulated by insulin signaling, and FOXO1 was downregulated at the mRNA level while its inactivation through phosphorylation increased. FOXO1 phosphorylation initiates the expression of the lipogenesis-activating transcription factor sterol regulatory element-binding protein 1 (SREBP1). SREBP1 levels were higher after PTEN knockdown and may account for the observed enhanced adipogenesis. To validate this, we overexpressed constitutively active FOXO1 in PTEN CRISPR cells and found reduced adipogenesis, accompanied by SREBP1 downregulation. We observed that PTEN CRISPR cells showed less senescence compared with controls and the senescence marker CDKN1A (p21) was downregulated in PTEN knockdown cells. Cellular senescence was the most significantly enriched pathway found in RNA-Seq of PTEN knockdown versus control cells. These results provide evidence that PTEN is involved in the regulation of APC proliferation, differentiation, and senescence, thereby contributing to aberrant adipose tissue growth in patients with PHTS., Competing Interests: Conflict of interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Background: Neoplasms of the retroperitoneum that contain a major fat component may represent either benign entities, such as lipomas or angiomyolipomas, or malignancy such as liposarcoma. Distinguishing these diagnoses has important implications for management. While liposarcomas often stain positively for MDM2 and CDK4 proteins, absence of these markers can lead to diagnostic and management challenges., Methods: We examined three cases in our institution of fat-containing masses of the retroperitoneum that lacked MDM2 and CDK4 markers to highlight the challenges in diagnosing and managing these cases. A thorough review of the literature examining radiologic and histologic features that can be used to determine that diagnosis was conducted and summarized., Results: The three cases we present represent the three main diagnostic entities that can be found in among fatty tumors of the retroperitoneum: lipoma, angiomyolipoma, and liposarcoma. While radiologic features and analysis of histology helped to inform management, these cases in conjunction with the literature also illustrate the limitations of the diagnostic work up and importance also factoring the biologic behavior of the tumor in its management., Conclusion: Fat-containing tumors of the retroperitoneum that do not stain for MDM2 or CDK4 can pose a diagnostic challenge. Assessing radiologic and pathologic features in conjunction with the biologic behavior of these tumors should inform their management.

Although the morphologic diagnosis of hibernoma is usually straightforward, some hibernomas have atypical morphologic features, mimicking atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDLs). In addition, the multivacuolated brown fat cells may be mistaken for lipoblasts by pathologists, especially those without significant soft tissue tumor exposure. Thus, we continue to receive in consultation cases of hibernoma sent for MDM2 fluorescence in situ hybridization testing to exclude ALT/WDL. Testing hibernomas for MDM2 amplification, however, adds cost and delays the final diagnosis. Recently, we have noted expression of neprilysin (CD10, CALLA), a zinc-dependent metalloproteinase involved in the inactivation of various peptide hormones, in brown fat cells, and wished to explore the potential utility of this widely available, inexpensive ancillary test in the differential diagnosis of hibernoma. Formalin-fixed, paraffin-embedded tissue sections from well-characterized cases of hibernoma (n = 48), brown fat (n = 21), ALTs/WDLs (n = 17), pleomorphic liposarcomas (PLPSs) (n = 6), lipomas (n = 5), and fat necrosis (n = 5) were immunostained for CD10, using a commercially available antibody and routine laboratory protocols. CD10 expression was evaluated in both adipocytes and in surrounding stromal cells. The hibernomas occurred in 28 men and 20 women, ranging from 11 to 76 years of age and involved the extremities (n = 25), pelvis (n = 7), abdomen/pelvis/retroperitoneum (n = 7), head and neck region (n = 6), back (n = 2), and chest (n = 1). All showed diffuse, strong CD10 expression in multivacuolated brown fat cells and in the majority of adjacent univacuolated fat cells. Brown adipose tissue from various anatomic structures showed an identical pattern of immunoreactivity. In contrast, CD10 expression was present in the adipocytes of only 3 of 17 (18%) ALTs/WDLs and was absent in lipomas and fat necrosis. Lipoblasts expressed CD10 in 3 PLPSs. Expression of CD10 by surrounding fibroblastic stromal cells was more widespread, present in 13 hibernomas, 10 ALTs/WDLs, 1 instance of fat necrosis, 6 PLPSs, and 4 examples of brown fat. We conclude that immunohistochemistry for CD10 may represent a useful, rapid and inexpensive ancillary test in the differential diagnosis of hibernoma from potential morphologic mimics, especially when morphologic features favor hibernoma. CD10 expression in adipocytes, however, should be rigorously distinguished from fibroblastic stromal cell CD10 expression, a nonspecific finding., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Background: Elucidation of lipid metabolism and accumulation mechanisms is of paramount importance to understanding obesity and unveiling therapeutic targets. In vitro cell models have been extensively used for these purposes, yet, they do not entirely reflect the in vivo setup. Conventional lipomas, characterized by the presence of mature adipocytes and increased adipogenesis, could overcome the drawbacks of cell cultures. Also, they have the unique advantage of easily accessible matched controls in the form of subcutaneous adipose tissue (SAT) from the same individual. We aimed to determine whether lipomas are a good model to understand lipid accumulation., Methods: We histologically compared lipomas and control SAT, followed by assessment of the lipidome using high-resolution 1 H NMR spectroscopy and ESI-IT mass spectrometry. RNA-sequencing was used to obtain the transcriptome of lipomas and the matched SAT., Results: We found a significant increase of small-size (maximal axis < 70 µm) and very big (maximal axis > 150 µm) adipocytes within lipomas. This suggests both enhanced adipocyte proliferation and increased lipid accumulation. We further show that there is no significant change in the lipid composition compared to matched SAT. To better delineate the pathophysiology of lipid accumulation, we considered two groups with different genetic backgrounds: (1) lipomas with HMGA2 fusions and (2) without gene fusions. To reduce the search space for genes that are relevant for lipid pathophysiology, we focused on the overlapping differentially expressed (DE) genes between the two groups. Gene Ontology analysis revealed that DE genes are enriched in pathways related to lipid accumulation., Conclusions: We show that the common shared lipid accumulation mechanism in lipoma is a reduction in lipolysis, with most gene dysregulations leading to a reduced cAMP in the adipocyte. Superficial lipomas could thus be used as a model for lipid accumulation through altered lipolysis as found in obese patients.

Few human cell strains are suitable and readily available as in vitro adipocyte models. We used resected lipoma tissue from a patient with germline phosphatase and tensin homolog (PTEN) haploinsufficiency to establish a preadipocyte cell strain termed LipPD1 and aimed to characterize cellular functions and signalling pathway alterations in comparison to the established adipocyte model Simpson-Golabi-Behmel-Syndrome (SGBS) and to primary stromal-vascular fraction cells. We found that both cellular life span and the capacity for adipocyte differentiation as well as adipocyte-specific functions were preserved in LipPD1 and comparable to SGBS adipocytes. Basal and growth factor-stimulated activation of the PI3 K/AKT signalling pathway was increased in LipPD1 preadipocytes, corresponding to reduced PTEN levels in comparison to SGBS cells. Altogether, LipPD1 cells are a novel primary cell model with a defined genetic lesion suitable for the study of adipocyte biology.

PIK3CA-related overgrowth spectrum is caused by mosaicism mutations in the PIK3CA gene. These mutations, which are also observed in various types of cancer, lead to a constitutive activation of the PI3K/AKT/mTOR pathway, increasing cell proliferation. Heat shock transcription factor 1 (HSF1) is the major stress-responsive transcription factor. Recent findings indicate that AKT phosphorylates and activates HSF1 independently of heat-shock in breast cancer cells. Here, we aimed to investigate the role of HSF1 in PIK3CA-related overgrowth spectrum. We observed a higher rate of proliferation and increased phosphorylation of AKT and p70S6K in mutant fibroblasts than in control cells. We also found elevated phosphorylation and activation of HSF1, which is directly correlated to AKT activation. Specific AKT inhibitors inhibit HSF1 phosphorylation as well as HSF1-dependent gene transcription. Finally, we demonstrated that targeting HSF1 with specific inhibitors reduced the proliferation of mutant cells. As there is currently no curative treatment for PIK3CA-related overgrowth spectrum, our results identify HSF1 as a new potential therapeutic target., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 The Authors. Published by Elsevier Inc. All rights reserved.)

Objective: Lumbosacral lipomas (LSLs), one form of closed spinal dysraphism, are congenital disorders of the terminal spinal cord (SC). Delayed neurologic deterioration often occurs in the subsequent developmental course of the patient. Identifying the cellular and molecular factors underlying the progressive damage to neural structures is a prerequisite for developing treatment strategies for LSLs., Methods: Nine LSL specimens obtained from the SC/lipoma interface during surgical resection were examined. Normal SC tissue served as a control. Clinical characteristics were obtained, and spinal magnetic resonance imaging was re-evaluated. Cellular marker profiles were established. Immunoreactivity (IR) of hypoxia-inducible factor 1α (HIF-1α/-2α), erythropoietin (Epo)/erythropoietin receptor (EpoR), interleukin-1β (IL-1β)/IL-1R1, and tumor necrosis factor α/tumor necrosis factor receptor type 1 were analyzed qualitatively and semiquantitatively by densitometry. Colabeling with cellular markers was determined by multifluorescence labeling. Cytokines were further analyzed by real-time reverse transcription polymerase chain reaction., Results: LSL specimens showed significant gliosis. HIF-1α/HIF-2α-IR and Epo/Epo-IR were found at significantly higher levels in the LSL specimens, as were IL-1β-/IL-1β receptor type 1 (IL1-R1) and tumor necrosis factor α/tumor necrosis factor receptor type 1 (P < 0.001), than were the controls. At the messenger RNA level, cytokines appeared partially induced. Double immunofluorescence labeling confirmed the costaining of these factors with inflammatory and glial markers., Conclusions: The expression of hypoxia-related and inflammatory mediators was shown for the first time in LSL specimens. These factors might play a role in multifactorial secondary lesion cascades underlying further damage to the neural placode in closed dysraphism., (Copyright © 2020 Elsevier Inc. All rights reserved.)

White adipose tissue browning has emerged as a putative therapy of obesity, and studies in mice have shown that Cdkn2a is implicated in white-to-brown transition. However, the role of Cdkn2a product p16 has been never studied in human brown fat tissue. The aim of the study is to investigate the expression of p16 in normal brown fat and in hibernoma, a lipoma containing brown fat-like adipocytes. Ten normal brown fat tissues and 5 hibernomas were immunohistochemically studied for p16 expression. Nearby white adipose tissue was used for comparison. All brown fat and hibernomas specimens express p16 in a cytoplasmic manner. Neighboring white adipose tissue is negative for p16 expression. Thus, cytoplasmic p16 may be associated with fat tissue browning.

Objective: The aim of this study was to investigate the immunohistochemical stain profiling of adipocytic tumors., Methods: From our archive files between the years of 2012-2018, excised, formalin-fixed and paraffin-embedded adipocytic tumors were retrospectively screened and 61 subjects were selected. The gender, age, tumor location and tumor diameter were evaluated. The cases were investigated in terms of p16, CD34, MDM2 expression and clinicopathological information., Results: Of the 61 patients included in the study, we found that 2 had hibernoma, 4 had lipoblastoma, 14 had spindle cell lipoma (SCL), 10 had lipoma, 20 had atypical lipomatous tumor/well differentiated liposarcoma (ALT/WDL), and 11 had dedifferentiated liposarcoma (DDL). In terms of diameter, ALT/WDL and DDL were significantly different from the others (p=0.001, p=0.001, respectively). There was a significant difference between the groups according to the location (p=0.001). 35% (7/20) of ALT/WDLs were in the lower extremities (thighs) and 35% (7/20) were located in the retroperitoneal region. 70% of DDLs (7/11) were located in the retroperitoneum. When CD34 expression was evaluated among the groups, a significant difference was observed (p=0.001). CD34 was positive in 92.9% of SCL cases. p16 immunoreactivity was significantly different between the groups (p=0.001). p16 expression was observed in 50.5% of ALT / WDL cases and 79% of DDL cases., Conclusion: p16 and CD34 expression are valuable in the differential diagnosis of lipomatous tumors when radiological and clinical considerations do not help to differential diagnosis of adipocytic tumors., Level of Evidence: Level IV, Therapeutic Study.

Background: The mechanistic (or mammalian) target of rapamycin (mTOR), a Ser/Thr kinase, associates with different subunits forming two functionally distinct complexes, mTORC1 and mTORC2, regulating a diverse set of cellular functions in response to growth factors, cellular energy levels, and nutrients. The mechanisms regulating mTORC1 activity are well characterized; regulation of mTORC2 activity, however, remains obscure. While studies conducted in Dictyostelium suggest a possible role of Ras protein as a potential upstream regulator of mTORC2, definitive studies delineating the underlying molecular mechanisms, particularly in mammalian cells, are still lacking., Methods: Protein levels were measured by Western blotting and kinase activity of mTORC2 was analyzed by in vitro kinase assay. In situ Proximity ligation assay (PLA) and co-immunoprecipitation assay was performed to detect protein-protein interaction. Protein localization was investigated by immunofluorescence and subcellular fractionation while cellular function of mTORC2 was assessed by assaying extent of cell migration and invasion., Results: Here, we present experimental evidence in support of the role of Ras activation as an upstream regulatory switch governing mTORC2 signaling in mammalian cancer cells. We report that active Ras through its interaction with mSIN1 accounts for mTORC2 activation, while disruption of this interaction by genetic means or via peptide-based competitive hindrance, impedes mTORC2 signaling., Conclusions: Our study defines the regulatory role played by Ras during mTORC2 signaling in mammalian cells and highlights the importance of Ras-mSIN1 interaction in the assembly of functionally intact mTORC2.

Spindle cell lipomas are a rare subtype of lipoma typically occurring in the shawl region of middle-aged men with a characteristic histological appearance consisting of mature adipocytes, ropey collagen and spindle cells. Those of extraordinary size or atypical anatomic location require a proper immunohistological workup to rule out more ominous malignancy. The authors report the rare presentation of a 54-year-old man with a large mass of the left palm causing discomfort and paresthesia for 6 months. Radiographs showed a radiolucent mass without mineralisation or bony involvement. MRI demonstrated a non-contrast-enhancing homogeneous lipomatous mass encompassing flexor tendons of the palm. Elective excisional biopsy and immunohistological analysis were consistent with spindle cell lipoma measuring 11 cm × 7 cm × 4 cm. This case is the largest spindle cell lipoma of the hand reported in the literature and appears to be the largest described in the upper extremity., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Limited 2019. No commercial re-use. See rights and permissions. Published by BMJ.)

The low-fat and fat-free spindle cell lipomas (SCLs) are rare and often mistaken for other benign and malignant morphological mimics, because of the fact that the diagnosis relies on its non-lipogenic component analysis. Here, we report the clinicopathological features of two oral SCLs (low-fat and fat-free variants). Both lesions presented clinically as an asymptomatic nodule, which initially yielded diagnostic difficulties on the morphological analysis alone. One case was diagnosed as low-fat SCL on the lower lip in a 29-year-old man, and the other as fat-free SCL on the buccal mucosa in a 46-year-old man. In both cases, immunohistochemistry showed strong positivity for CD34 and, remarkably, retinoblastoma (Rb) protein was deficient. Mast cell (MC) tryptase and toluidine blue stain highlighted numerous MCs distributed throughout all tumor stroma. Alpha-SMA and desmin were negative. S100 evidenced scarce adipocytes only in the low-fat SCL case. Conservative surgical treatment was performed and no recurrence was noticed in about 2-year of follow-up in both cases. Because of the potential pitfalls, careful morphological analysis of the tumor stroma in the low-fat/fat-free SCL diagnosis, supported by immunohistochemistry (especially CD34, Rb and MC tryptase), is strongly recommended. To the best of our knowledge, these are the first and second cases reported of fat-free and low-fat SCL in the oral cavity., (© 2019 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)

Immunomodulatory and wound healing activities of adipose-derived stem cells (ADSCs) have been reported in various in vitro and in vivo experimental models suggesting their beneficial role in regenerative medicine and treatments of inflammatory-related disorders. Lipoma-derived stem cells (LDSCs) were reported as a potential tool in regenerative medicine due to the similarity with ADSCs but we have previously shown that LDSCs have different differentiation capacity than ADSCs despite a similar mesenchymal phenotype. To further analyze the potential differences and/or similarities between those two stem cell types, in the present study we examined the macrophages (MΦs)' response, immunomodulatory and wound healing effect of conditioned media (CM) of LDSCs and ADSCs in indirect co-culture system in vitro. We confirmed similar mesenchymal phenotype and stemness state of LDSCs and ADSCs but indicated differences in expression of some inflammatory-related genes. Anti-inflammatory potential of CM of LDSCs and ADSCs, with pronounced effect of LDSCs, in unstimulated RAW 264.7 MΦs was evaluated by decrease in Tnf and increase in Il10 gene expression, which was confirmed by corresponding cytokines' secretion analysis. Conditioned media of both LDSCs and ADSCs led to the functional activation of MΦs, with slightly more pronounced effect of CM of LDSCs, while both stimulated wound healing in vitro in a similar manner. Results of this study suggest that LDSCs secrete soluble factors like ADSCs and therefore may have a potential for application in regenerative medicine, due to immunomodulatory and wound healing activity, and indicate that LDSCs through secretome may interact with other cells in lipoma tissue.

Lipofibromatosis is a rare pediatric soft tissue tumor with predilection for the hands and feet. Previously considered to represent "infantile fibromatosis", lipofibromatosis has distinctive morphological features, with mature adipose tissue, short fascicles of bland fibroblastic cells, and lipoblast-like cells. Very little is known about the genetic underpinnings of lipofibromatosis. Prompted by our finding of the FN1-EGF gene fusion, previously shown to be a characteristic feature of calcifying aponeurotic fibroma (CAF), in a morphologically typical case of lipofibromatosis that recurred showing features of CAF, we studied a cohort of 20 cases of lipofibromatosis for this and other genetic events. The cohort was composed of 14 males and 6 females (median age 3 years; range 1 month-14 years). All primary tumors showed classical lipofibromatosis morphology. Follow-up disclosed three local recurrences, two of which contained calcifying aponeurotic fibroma-like nodular calcifications in addition to areas of classic lipofibromatosis, and no metastases. By FISH and RNA sequencing, four cases were positive for FN1-EGF and one case each showed an EGR1-GRIA1, TPR-ROS1, SPARC-PDGFRB, FN1-TGFA, EGFR-BRAF, VCL-RET, or HBEGF-RBM27 fusion. FN1-EGF was the only recurrent fusion, suggesting that some cases of "lipofibromatosis" may represent calcifying aponeurotic fibroma lacking hallmark calcifications. Several of the genes involved in fusions (BRAF, EGFR, PDGFRB, RET, and ROS1) encode receptor tyrosine kinases (RTK), or ligands to the RTK EGFR (EGF, HBEGF, TGFA), suggesting a shared deregulation of the PI3K-AKT-mTOR pathway in a large subset of lipofibromatosis cases.

Spindle cell/pleomorphic lipomas (SCLs), cellular angiofibromas (CAFs) and mammary-type myofibroblastomas (MFBs) are rare benign mesenchymal tumors with monoallelic 13q14 deletion. They are predicted to have a common pathogenic mechanism due to shared similar histological and immunohistochemical features; however, pathological consequences of monoallelic 13q14 deletion remain unknown. We previously reported a CAF case with monoallelic 13q14 deletion in which the tumor expressed decreased levels of FOXO1 and RB1, both of which were encoded in 13q14, and increased reactive oxygen species (ROS) levels. We further demonstrated the activation of p38 mitogen-activated protein kinase (p38 MAPK) pathway induced by oxidative stress. We hypothesized that SCLs, CAFs and MFBs would share common molecular signatures involving FOXO1, ROS and p38 MAPK and that their expression patterns were different from those tumors without monoallelic 13q14 deletion such as solitary fibrous tumors (SFTs). We compared the expression levels of FOXO1, RB1, ROS markers and several signal transduction factors between SCLs and SFTs. SCLs expressed decreased levels of FOXO1 and RB1, whereas SFTs showed no change. Both tumor types exhibited increased markers of ROS; however, nuclear localization of phosphorylated p38 was significantly more frequent in SCLs than that in SFTs, suggesting p38 MAPK activation by oxidative stress. SFTs showed lower p38 MAPK activity and higher β-catenin expression, implying that oxidative stress was caused by increased cellular proliferation stress. Finally, CAFs and MFBs showed changes similar to those observed in SCLs. Overall, tumors with monoallelic 13q14 deletion showed shared molecular signatures that might be associated with pathogenesis.

Background: Lipomas are common benign soft tissue tumors that are well-circumscribed and encapsulated. However, adipose masses that are not demarcated from the surrounding fat are often encountered. Two distinct types of lipomas were analyzed from surgical perspective., Methods: Thirty patients were enrolled after lipoma excision and diagnosed with either encapsulated (n = 20) or non-encapsulated lipoma (n = 10). Comparison of clinical variables, histologic analyses and characterization of the lipoma adipose-derived stem cells (ASCs) between the two lipomas were performed., Results: Non-encapsulated lipomas were associated with older age at operation, larger tumor and increased seroma formation. The density of lymphatic vessels and gene expressions related to lymphatic vessel, inflammation and proliferation were increased in non-encapsulated lipoma. ASCs of non-encapsulated lipoma showed enhanced proliferation when cultured with serum., Conclusions: Non-encapsulated lipomas and their ASCs showed distinct lymphatic histology and cellular response. These findings elucidated the pathogenesis and pathophysiology of lipomas.

Adipose tissue tumors (lipomas) frequently develop in patients with heterozygous germ line phosphatase and tensin homolog (PTEN) mutations. simvastatin has been demonstrated to exhibit antitumor effects, and so the aim of the present study was to assess the effects of simvastatin on the growth of human PTEN haploinsufficient lipoma cells. Whether the effects of simvastatin in lipomas are mediated via PTEN upregulation was also assessed. The results of the present study revealed that simvastatin treatment reduced cell viability and induced apoptosis in human lipoma cells. Furthermore, it was demonstrated that the expression of cellular PTEN mRNA and protein was increased following simvastatin stimulation. In addition, the phosphorylation of protein kinase B and downstream targets of mammalian target of rapamycin and 4E‑binding protein (4E‑BP)‑1 was attenuated. It was also demonstrated that simvastatin induced PTEN transcriptional upregulation by increasing peroxisome proliferator‑activated receptor (PPAR)γ expression. The small interfering RNA‑mediated knockdown of PPARγ abrogated the stimulatory effect of simvastatin on the PTEN protein, but did not influence apoptosis. The results of the present study suggest that simvastatin may be beneficial for patients with inoperable PTEN haploinsufficient lipomas.

Background: The metabolic and immunologic properties of adipose tissue are linked to the pathogenesis of type 2 diabetes mellitus. Lipomatous tumors, such as liposarcomas, are rare but can reach significant size. We hypothesized that some lipomatous tumors are metabolically active and can alter systemic glucose homeostasis., Methods: We performed a retrospective study of patients who underwent resection of a lipomatous tumor at a tertiary cancer referral center (2004-2015). We divided patients into nondiabetics, well-controlled diabetics (hemoglobin A1c [HbA1c] < 7), and poorly controlled diabetics (HbA1c ≥ 7). We compared patient demographics, tumor characteristics, and measures of glycemic control among these groups before and after tumor resection., Results: We reviewed 217 operations for lipomatous tumors. No differences were observed in tumor characteristics in patients with and without diabetes. However, tumor characteristics differed significantly between the well-controlled and poorly controlled diabetics groups. Patients with poorly controlled diabetes had larger tumors that were more likely to be malignant, retroperitoneal, and well-differentiated. Tumor resection had no detectable impact on diabetes, as assessed by HbA1c, and requirement for diabetic medications., Conclusions: Poorly controlled diabetes was linked to the presence of large, malignant, and retroperitoneal lipomatous tumors. However, in limited follow-up, no detectable impact of tumor resection was apparent on glycemic control. These data suggest that most lipomatous tumors do not exert a clinically relevant impact on glucose homeostasis., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Tofacitinib is an oral JAK inhibitor for the treatment of rheumatoid arthritis. In the 2-year carcinogenicity study with tofacitinib, increased incidence of hibernoma (a neoplasm of brown adipose tissue [BAT]) was noted in female rats at ≥30 mg/kg/day (≥41x human exposure multiples). Thus, signaling pathways within BAT were investigated by measuring BAT: weight, cell proliferation biomarkers, content of basal and prolactin-induced phosphorylated Signal Transducer and Activator of Transcription (STAT), and uncoupling protein 1 (UCP-1). The relationship between cardiovascular hemodynamics and plasma norepinephrine (NE) levels was also investigated. Tofacitinib administered to female rats at doses of 10, 30, or 75 mg/kg/day for 14 days increased BAT weight at 75 mg/kg/day and cell proliferation at ≥30 mg/kg/day. JAK inhibition, observed as lower pSTAT3 and pSTAT5 in BAT, was noted at ≥10 mg/kg/day, while lower activity of BAT was observed as lower UCP-1 protein at ≥30 mg/kg/day. In cultured brown adipocytes, prolactin-induced increase in pSTAT5 and pSTAT3 were inhibited by tofacitinib in a concentration-dependent manner. Tofacitinib lowered blood pressure, increased heart rate, and resulted in dose-dependent increases in circulating NE. Thus, JAK/STAT inhibition in BAT and sympathetic stimulation are two factors which might contribute to the genesis of hibernomas by tofacitinib in rats., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Spindle cell lipoma (SCL) is a benign neoplasm of the adipose tissue that may resemble an undifferentiated soft tissue sarcoma (STS). This report describes the histopathological features of 6 SCLs in dogs. All SCLs were located in the subcutis and were composed of bland, occasionally vacuolated spindle cells intermixed with ropey collagen and myxoid matrix. Sudan IV stain performed in 1 case demonstrated the lipid content of vacuoles. Mature adipocytes represented less than 10% of the neoplasm in 3 cases and were absent in the remaining 3. Average mitotic count in 10 high-power fields was 0.17. Neoplastic cells were immunohistochemically positive for vimentin and negative for S100 protein, smooth muscle actin, factor VIII-ra, and MDM2. Awareness of SCL and its specific histopathological features is essential to diagnose this specific tumor. Further studies are needed to document the biological behavior of these tumors in dogs.

Introduction: Lipoma is the most familiar soft-tissue tumor. But the etiology of lipoma remains imprecise. Sex steroid hormones such as estrogen have effects on muscle and adipose tissue development. There is now significant evidence that sex steroids are involved in the site specificities of adipose tissue metabolism. This association of adipose tissue metabolism between sex steroid hormones suggests a possible role for sex steroids in the pathogenesis of lipoma., Methods: To investigate this concept, the authors evaluated the expression of the estrogen receptor (ER) and the progesterone receptor (PR) in soft tissue lipoma in this study.In addition, angiogenesis and the production of angiogenic factors are fundamental for tumor progression in the form of growth, invasion, and metastasis. Epidermal growth factor receptor (EGFR) is involved in a signaling cascade that influences proliferation and other tumor-promoting activities. In this respect, the authors tried to define the correlation of soft tissue lipoma tumor cell and specific 2 immunohistologic markers, vascular endothelial growth factor (VEGF) and EGFR.The study population included patients who diagnosed with soft tissue lipoma, 20 independent patients were selected. All specimens were stained with hematoxylin and eosin. All slides were examined by a pathologist under a microscope. ER, PR, VEGF, and EGFR expression was analyzed by immunohistochemistry., Result: ER, PR, and EGFR of tumor cell had significantly more negative than positive. And VEGF of tumor cell had significantly more positive than negative. There was no significantly difference between site of tumor and immunohistochemical stain., Discussion and Conclusion: There are only a few studies for ER and PR in soft tissue related tumors. The authors estimated that the abnormal local proliferation and accumulation of adipocyte in soft tissue lipoma is related to sex steroid hormone action, especially estrogen and progesterone. But ER and PR of tumor cell had significantly more negative than positive in this study. The authors concluded that estrogen and progesterone are not impact factor of pathogenesis of soft tissue lipoma. Vascular endothelial growth factor of tumor cell had significantly more positive than negative. Angiogenesis is an essential factor for tumor growth. The VEGF expression of soft tissue lipoma can be understood in the same context. The authors need more study to reveal an association between lipoma and EGFR, because some patients of lipoma were positive to EGFR in this study.

Angiomyofibroblastoma is a rare and benign tumor that usually involves vulvovaginal area in women of reproductive age and early menopause. We report a lipomatous angiomyofibroblastoma in a 55-year-old multigravid woman. This tumor measured 9 cm in size and contained prominent mature adipose tissue that comprised approximately 50% of the tumor.

Spindle cell lipoma (SCL) and pleomorphic lipoma constitute a spectrum of lipomatous lesions with distinctive clinicopathological features. Multiple variants of SCL have been reported including fibrous, plexiform, vascular, pseudoangiomatous, low-fat/fat-free, and myxoid changes. This paper describes an unusual patient with a 1-cm submucosal nodular lesion excised from the buccal mucosa of a 55-year-old woman with classic histopathological and immunohistochemical features of "low-fat" plexiform SCL with prominent myxoid stroma, which initially suggested a soft-tissue myxomatous lesion other than SCL. The current lesion exhibited microscopically few adipocytes supported by network-like myxoid proliferations with retraction artifacts from the surrounding stromal connective tissue. Immunohistochemistry was positive for vimentin, CD34, CD10, and S100, the latter only on adipocytes. The Ki-67 was <1%. Pan-cytokeratin (AE1/AE3), desmin, alpha-SMA, EMA, bcl-2, p53, and remarkably retinoblastoma protein (pRb) were negative. "Low-fat" plexiform SCL bear no significant prognostic significance, but this lesion may challenge the diagnosis even experienced pathologists.

Although most cases of atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) can be diagnosed solely on the basis of histologic features, those lacking diagnostic histologic features require ancillary studies for accurate classification. Fluorescent in situ hybridization (FISH) for amplification of MDM2 has been considered the gold standard for diagnosis in these situations. Immunostaining for MDM2 and/or CDK4 has been adopted as a surrogate method because of its high concordance rate with FISH and lower cost. However, studies examining the concordance of the 2 methods have been based preferentially on cases in which the diagnosis could be established histologically. No study has explored the concordance between the 2 methods in histologically ambiguous cases or in cases in which the diagnosis of ALT/WDL is not apparent after a review of all slides. To address this, we performed immunostaining for MDM2 and CDK4 on 183 well-differentiated lipomatous tumors that could not be diagnosed on purely histologic grounds and that were, therefore, subjected to FISH analysis. These included ALT/WDLs (n=56), lipomas (n=96), and lipoma variants (n=31). Staining for MDM2 and CDK4 was noted in 25/56 and 23/56 ALT/WDL, respectively, giving a sensitivity of 45% and 41% and a specificity of 98% and 92%. Staining was noted exclusively in the nuclei of atypical cells and not in the nuclei of adipocytes. Staining for MDM2 and CDK4 occurred in 2/125 and 10/117 benign lipomatous lesions, respectively. False-positive staining was equivalent in intensity to ALT/WDL. We conclude that MDM2 and CDK4 staining is a relatively insensitive method for diagnosing ALT/WDL in cases that are histologically ambiguous, as staining is restricted to neoplastic cells with atypia that are underrepresented in these cases. Therefore, in cases like ours that closely simulate clinical practice, FISH is the more reliable and cost-effective option.

Objectives: Spindle cell lipomas (SCLs) are benign lipomatous neoplasms that classically arise in the posterior neck, upper back, and shoulders of older male patients. We sought to characterize the occurrence of this entity at nonclassic sites., Methods: All cases of SCL arising at atypical sites were retrieved from our archives., Results: Of 439 total cases of SCL, 57 arose at atypical locations in 32 men and 25 women (age range, 27-79 years). The tumor sites included leg (n = 23), buttock/perineum/inguinal (n = 10), forearm (n = 9), finger (n = 9), foot (n = 2), toe (n = 2), hand (n = 1), and flank (n = 1). CD34 was positive staining in all cases tested (52/52), while desmin was negative in most tumors (48/50). Thirty-eight of 38 cases tested exhibited loss of Rb expression. No cases showed CPM/MDM2 amplification (0/48). No local recurrences have been reported (n = 39)., Conclusions: SCLs may arise in the trunk, lower extremities, and distal upper extremities. While most SCLs arising in classic sites occur in male patients, there is a relatively equal sex distribution in tumors at atypical sites. Pathologists should be aware that SCLs arise at atypical locations to avoid misclassification as other lipomatous neoplasms, including atypical lipomatous tumor., (© American Society for Clinical Pathology, 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Spindle cell lipoma represents a distinct clinicopathological entity and is related to cellular angiofibroma and mammary-type myofibroblastoma. Spindle cell lipomas are composed of mature lipogenic cells and a variable number of CD34-positive spindle cells that show loss of retinoblastoma protein expression. Spindle cell lipomas occasionally express S-100 protein. We studied one case of purely dermal spindle cell lipoma and four cases of classical subcutaneous spindle cell lipoma arising in one female and four male patients (age ranged from 55 to 69 years). The neoplasms arose on the nose, the chin, the neck, the forehead and retroauricular, and all lesions had been marginally or incompletely excised. The studied cases showed classical histological and immunohistochemical features of spindle cell lipoma and, in addition, strong expression of S-100 protein by spindle-shaped tumour cells. S-100-expression in spindle cell lipoma may cause problems in the differential diagnosis with neural and melanocytic neoplasms and emphasizes the plasticity of the spindle cells in spindle cell lipoma.

Spindle cell myoepithelioma with extensive lipomatous metaplasia and thick collagen bundles has not yet been described, and there are no published reports on its cytological appearance in fine-needle aspiration (FNA). A 49-year-old man presented with a painless mass in the right submandibular area that had been gradually enlarging for a period of 5 years. The cytologic smears showed fascicles of cohesive spindle cells as well as individual bland cells with bipolar naked nuclei in a fibrillary background. Brightly eosinophilic bundles were intermingled with spindle cells and fat-like vacuoles. The FNA results were suggestive of neurogenic tumor. Patient underwent submandibular gland resection. Grossly, the cut surface showed a well-encapsulated, yellowish-white, soft, elastic mass, measuring 2.8 × 1.9 × 1.5 cm. The tumor consisted of uniform bland spindle cells arranged in short fascicles admixed with adipocyte-like cells and transversing thick collagen bundles, which demonstrated immunoreactivity for myoepithelial markers and ultrastructural features characteristic of myoepithelial cells, suggesting the presence of lipomatous metaplasia. The FNA cytology of spindle cell myoepithelioma with extensive lipometaplasia mimicked that of neurogenic tumor or lipomatous mesenchymal tumor. This case represents the first description of submandibular gland myoepithelioma with lipometaplasia, which is characterized by the coexistence of spindle cells, collagen bundles, and fat-like vacuoles in a fibrillary background. Diagn. Cytopathol. 2016;44:764-769. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

We have studied 22 cases of mammary lipophyllodes tumors (LPT), analyzing their clinicopathologic features along with available follow-up. All cases were tested for cytokeratins, S100 protein, and MDM2, and in selected cases for estrogen receptor, smooth muscle actin, bcl2, desmin, and myogenin. Patients were women aged 21 to 69 years (average, 45 years), and LPT size ranged from 1.6 to 30 cm (average, 9.7 cm). Microscopically, LPT segregated as follows: atypical lipoma-like tumor/well-differentiated liposarcoma (ALT/WDL), 8 cases; myxoid, 6; and pleomorphic/poorly differentiated/round cell, 8, including a case of dedifferentiated liposarcoma. Immunohistochemistry studies showed focal positive staining for S100 and CD34 in most ALT/WDL, and desmin and myogenin in 2 cases with evidence of rhabdomyoblastic differentiation. MDM2 positivity was focally seen in 1 case. Follow-up was available in 8 cases. Multiple recurrent tumors were seen in 2 patients, and metastatic disease to the lung was seen in 2 patients. In 4 patients with a follow-up between 2 and 15 years there was no evidence of recurrent or metastatic disease. Patients with ALT/WDL (2/2) were alive with no evidence of disease; 2 of 4 patients with myxoid liposarcoma component experienced tumor recurrence, whereas pleomorphic liposarcoma LPT pursued a less favorable course although only 1 patient died of the condition. Absence of MDM2 reactivity in most cases seems not as meaningful as in fatty tumors of somatic soft parts., (Copyright © 2015 Elsevier Inc. All rights reserved.)

A 67-year-old woman presented with progressive enlargement of a long-standing mass on the surface of her OS associated with ocular surface irritation. The mass was excised en bloc. Histopathological examination showed a well-defined encapsulated tumor composed of wiry collagen containing bland spindle cells that were strongly positive for CD34 with scattered mature adipocytes. These features confirmed a diagnosis of spindle cell lipoma.

Patients with phosphatase and tensin homolog (PTEN) hamartoma tumor syndrome and germline mutations in PTEN frequently develop lipomatosis, for which there is no standard treatment. Rapamycin was shown to reduce the growth of lipoma cells with heterozygous PTEN deficiency in vitro, but concomitantly induced an upregulation of AKT phosphorylation. Since it was shown that resveratrol stabilizes PTEN, we asked whether co-incubation with resveratrol could suppress the rapamycin-induced AKT phosphorylation in PTEN-deficient lipoma cells. Resveratrol incubation resulted in decreased lipoma cell viability by inducing G1-phase cell cycle arrest and apoptosis. PTEN expression and AKT phosphorylation were not significantly changed, whereas p70S6 kinase (p70S6K) phosphorylation was reduced in PTEN-deficient lipoma cells after resveratrol incubation. Rapamycin/resveratrol co-incubation significantly decreased viability further at lower doses of resveratrol and resulted in decreased p70S6K phosphorylation compared to rapamycin incubation alone, suggesting that resveratrol potentiated the growth inhibitory effects of rapamycin by reducing p70S6K activation. Both viability and p70S6K phosphorylation of primary PTEN wild-type preadipocytes were less affected compared to PTEN-deficient lipoma cells by equimolar concentrations of resveratrol. These results support the concept of combining chemopreventive natural compounds with mammalian target of rapamycin (mTOR) inhibitors to increase the efficacy of chemotherapeutic drugs for patients suffering from overgrowth syndromes.

Spindle cell lipoma (SCL) is an uncommon variant of lipoma that usually is present in subcutaneous fat of adult men. This tumor has a low rate of local recurrence and no risk of malignant behavior. Although histological features of SCL are well documented, cytological descriptions have been few. We present the case of a 41-year man with a right arm swelling, which on fine-needle aspiration cytology showed adipose tissue fragments, spindle cell areas mimicking benign nerve sheath tumor, and bundles of ropy collagen in a myxoid background, suggesting a diagnosis of SCL. SCL with predominant spindle cell component may mimic benign nerve sheath tumor on aspiration cytology. Subtle cytological features like presence of adipose tissue, ropy collagen, and mast cells help in accurate diagnosis., (© 2015 Wiley Periodicals, Inc.)

The Rb and Pten tumor suppressor genes are important regulators of bone development and both are frequently mutated in the bone cancer osteosarcoma (OS). To determine if Rb1 and Pten synergize as tumor suppressor genes for osteosarcoma, we co-deleted them in osteoprogenitor cells. Surprisingly, we observed rapid development of adipogenic but not osteosarcoma tumors in the ΔRb1/Pten mice. ΔPten solo deleted mice also developed lipoma tumors but at a much reduced frequency and later onset than those co-deleted for Rb1. Pten deletion also led to a marked increase in adipocytes in the bone marrow. To better understand the function of Pten in bone development in vivo, we conditionally deleted Pten in OSX(+) osteoprogenitor cells using OSX-Cre mice. μCT analysis revealed a significant thickening of the calvaria and an increase in trabeculae volume and number in the femur, consistent with increased bone formation in these mice. To determine if Pten and Rb1 deletion actively promotes adipogenic differentiation, we isolated calvarial cells from Pten(fl/fl) and Pten(fl/fl); Rb1(fl/fl) mice, infected them with CRE or GFP expressing adenovirus, treated with differentiation media. We observed slightly increased adipogenic, and osteogenic differentiation in the ΔPten cells. Both phenotypes were greatly increased upon Rb1/Pten co-deletion. This was accompanied by an increase in expression of genes required for adipogenesis. These data indicate that Pten deletion in osteoblast precursors is sufficient to promote frequent adipogenic, but only rare osteogenic tumors. Rb1 hetero- or homo-zygous co-deletion greatly increases the incidence and the rapidity of onset of adipogenic tumors, again, with only rare osteosarcoma tumors.

Spindle cell lipoma is a histologically distinct variant of lipoma characteristically arising in the subcutis of the posterior neck, upper back, or shoulder. Spindle cell lipomas infrequently occur within the oral cavity and, in particular, rarely involve the tongue. The clinical and pathologic features of eight cases of spindle cell lipoma affecting the tongue were analyzed. The study group included five men and three women ranging in age from 35 to 80 years (mean 57.4 years). Most lesions presented as either a painless or slowly growing lingual mass. The tumors were well circumscribed and characterized microscopically by a mixture of mature adipocytes, cytologically bland spindle cells, and interspersed bundles of thick collagen fibers in variable proportions. Myxoid stroma was a prominent feature in three lesions. The spindle cells were positive with CD34, while negative with S-100 protein, desmin, and smooth muscle actin. Treatment consisted of local excision in all cases. There have been no recurrences to date, with clinical follow up information available for all patients (range 11-118 months; mean 50.8 months). Lingual examples of spindle cell lipoma should be distinguished from other fat containing spindle cell neoplasms that can arise at this anatomic site.

A 30-year-old otherwise healthy female patient presented to the oculoplastic service with complaints of gradually increasing proptosis and discomfort of the OD of about 4 months' duration. On imaging, an ill-defined mass was seen in the right orbit which, on biopsy, turned out to be a spindle cell lipoma. Lipomas, the commonest among the mesenchymal soft tissue tumors, are surprisingly of rare occurrence in the orbit, despite the presence of abundant fat in the intraorbital space. The authors describe the presentation, management, and outcome of a rare orbital pathology--an orbital spindle cell lipoma.