Atypical Spindle Cell/Pleomorphic Lipomatous Tumor

Atypical spindle cell/pleomorphic lipomatous tumor (ASCPLT) is a rare soft tissue neoplasm, commonly arising in the subcutis (more common than deep soft tissue) of limbs and limb girdles during mid-adulthood. ASCPLT is histologically a lipogenic neoplasm with ill-defined margins composed of a variable amount of spindle to pleomorphic/multinucleated cells within a fibromyxoid stroma. ASCPLTs lack MDM2 amplification, but a large subset show RB1 deletion and variable expression of CD34. Though initially thought to be the malignant form of spindle cell lipoma, ASCPLTs are benign with local recurrences (∼10-15%) and no well-documented dedifferentiation or metastasis.

A case of fat-forming solitary fibrous tumor that is prone to be confused with liposarcoma

Fat-forming solitary fibrous tumor is a rare and specific subtype of solitary fibrous tumor. In this case, a mass of 8.3 cm in diameter was found in a 59-year-old male patient's right retroperitoneum, as revealed by abdominal contrast-enhanced computed tomography (CT) images. The tumor exhibited a well-circumscribed nature and histological features characterized by a combination of hemangiopericytomatous vasculature and mature adipose tissue, comprising around 70% of the total tumor composition. Immunohistochemistry staining revealed diffuse positive expression of STAT6 and CD34 in the tumor cells. Based on these findings, the final diagnosis was determined to be a fat-forming solitary fibrous tumor located in the retroperitoneum. It is important to consider other potential differential diagnoses, including angiomyolipoma, dedifferentiated liposarcoma, spindle cell lipoma, and atypical lipomatous tumor/well-differentiated liposarcoma.

Intra-Abdominal and Retroperitoneal Benign Lipomatous Tumors-An Extremely Rare Mimic of Liposarcoma and its Diagnostic Challenge

Background. Lipomas are common superficial soft tissue tumors of mature adipocytes. In contrast, well-differentiated/dedifferentiated liposarcoma typically presents in the retroperitoneum as large masses. We provide clinicopathologic and follow-up details of 9 retroperitoneal/intra-abdominal benign lipomatous tumors (BLT) and discuss the utility of ancillary fluorescence in situ hybridization (FISH) in distinguishing from their malignant counterparts. Design. Clinicopathologic details and histology of 9 intra-abdominal and retroperitoneal lipomas were studied along with ancillary CD10 immunohistochemistry (IHC) and FISH for MDM2 and CDK4 amplification. Results. There were 6 females and 3 males. Median age at diagnosis was 52 years (range 36-81 years). Seven were identified incidentally and 2 presented with primary complaints. On imaging, 7 were considered suspicious for liposarcoma. Grossly, the tumors ranged from 3.4 to 41.2 cm (median 16.5 cm). Histologically, all cases showed well-differentiated BLT, further classified as lipoma (n = 7; 1 with metaplastic ossification, 2 with prominent vessels, and 4 ordinary lipomas) and lipoma-like hibernoma (n = 2)-the latter 2 showed intramuscular lesions with interspersed brown fat. CD10 IHC showed strong staining in the 2 hibernomas, whereas the staining was weak in the remaining. MDM2 and CDK4 amplification were negative by FISH in all. Follow-up (median 18 months) did not show recurrence on clinical or imaging evaluation. Conclusion. Retroperitoneal/intra-abdominal BLT are extremely rare and are indistinguishable clinically and radiographically from liposarcoma. This necessitates molecular confirmation even when the histology is convincingly benign, for a confident diagnosis. Our cohort shows that conservative excision without removal of abutted organs is sufficient in most cases.

A novel HMGA2::KITLG fusion in a dedifferentiated liposarcoma with amplification of MDM2 and HMGA2

High-mobility group AT-hook 2 (HMGA2) is rearranged in various types of mesenchymal tumors, particularly lipomas. HMGA2 is also co-amplified with mouse double minute 2 (MDM2) in well-differentiated liposarcoma/dedifferentiated liposarcoma (WDLPS/DDLPS). We report a case of relapsed DDLPS with a novel in-frame fusion between HMGA2 and KITLG, which encodes the ligand for KIT kinase, a critical protein involved in gametogenesis, hematopoiesis, and melanogenesis. The HMGA2 breakpoint is in intron 3, a commonly observed location for HMGA2 rearrangements, while the KITLG breakpoint is in intron 2, leading to a fusion protein that contains almost the entire coding sequence of KITLG. By immunohistochemical staining, tumor cells expressed KIT and showed phosphorylated MAPK, a major KIT downstream target. We suggest an oncogenic mechanism that involves the overexpression of KITLG caused by its rearrangement with HMGA2, leading to the constitutive activation of KIT kinase. While MDM2 amplification was observed in both the primary tumor and the relapsed tumor, the HMGA2::KITLG was only present in the relapsed tumor, indicating the role of HMGA2::KITLG in disease progression.

Case report: Pai syndrome with multiple ventricular septal defect and without cleft palate

Pai syndrome is described as the association of a midline cleft lip, midline facial polyps, and lipoma of the central nervous system. However, only a few patients present the full triad, and most exhibit a wide spectrum of phenotypic variability. Its entire clinical spectrum is still poorly delineated and the etiology remains unknown. In this report, a newborn was presented with congenital nasal septal lipoma, lipoma of the corpus callosum, multiple ventricular septal defect, and additional minor facial dysmorphism. This entity, multiple ventricular septal defect, which has never been reported in PS. Cytogenetic analysis showed normal male 46, XY karyotype. Chromosomal microarray analysis (750 K array) was also unremarkable. This case draws attention with the presence of multiple ventricular septal defect in Pai syndrome and is important in terms of providing phenotypic diversity. To our knowledge, this is also the first genetically evaluated case of Pai syndrome from Turkey.

Benign female genital tract smooth muscle tumors with adipocytic differentiation: A morphologic, immunohistochemical and MDM2 fluorescence in situ hybridization study of 44 conventional lipoleiomyomas and lipoleiomyoma variants

Leiomyomas with adipocytic differentiation typically occur in the uterus although they may arise at several sites in the female genital tract. While these are most commonly spindled leiomyomas with a component of adipocytic tissue ("conventional lipoleiomyomas"), there is a relatively ill-defined assortment of leiomyoma variants with adipocytic differentiation. We performed a morphologic, immunohistochemical and MDM2 gene amplification analysis of a large series of gynecologic leiomyomas with adipocytic differentiation to better define the clinicopathologic spectrum. Forty four tumors from 44 patients were identified and classified as conventional lipoleiomyoma (n = 21), adipocyte-rich lipoleiomyoma (defined as tumor volume >80 % adipocytes, n = 9); cellular lipoleiomyoma (n = 9); hydropic lipoleiomyoma (n = 3); and lipoleiomyoma with bizarre nuclei (n = 2). Patient age ranged from 32 to 83 years (mean 63; median 63). Primary location included uterine corpus (35), uterine cervix (3), uterine corpus/cervix (1), broad ligament (2), parametrium (2), and round ligament (1). Tumor size was 0.6-30 cm (mean 8; median 6). None of the 34 patients with follow up developed further disease (range 1-311 months; mean 65; median 41). Immunohistochemical expression of ER, PR, HMB45, Melan A, Cathepsin K and WT-1 in lipoleiomyomas and variants was similar to patterns in non-adipocytic gynecologic leiomyomas. MDM2 amplification fluorescence in situ hybridization performed on 14 tumors was negative in all. Our findings suggest female genital tract conventional lipoleiomyomas and lipoleiomyoma variants largely parallel their non-adipocytic counterparts in morphology and immunophenotype, and may be categorized using non-adipocytic leiomyoma histologic criteria.

Anisometric Cell/Dysplastic Lipomas in a Retinoblastoma Survivor: Report of a Case with Review of the Literature

Different authors have recently described a subtype of lipoma characterized by variation of adipocyte size, single cell fat necrosis, and a subset with minimal to mild nuclear atypia, and termed these as anisometric cell/dysplastic lipoma (AC/DL). These lipomas follow a benign course and rarely recur. In 3 examples, AC/DL has occurred in patients with childhood retinoblastoma (RB). We report another such example where multiple AC/DL occurred in the neck and back of a 30-year-old male who had germline RB1 gene deletion and bilateral RB in infancy. On excision, all tumors histologically showed similar morphology of adipocyte anisometry, focal single cell necrosis with surrounding binucleated or multinucleated histiocytes, hyperchromatic and minimally atypical lipocyte nuclei, vacuolated Lockhern change, rare foci of fibromyxoid change, occasional mononuclear cell clusters around capillaries, and loss of RB1 immunostaining. Unequivocal atypical cells, lipoblasts, floret-nucleated or multinucleated giant cells were absent. Molecular analysis of tumor cells showed monoallelic RB1 gene loss without amplification of MDM2 and CDK4 genes. Short-term follow up did not show tumor recurrence. AC/DLs in RB survivors are characterized by multiplicity, unifying histology, and benign course. Their biology appears distinct from ordinary lipomas, spindle cell lipomas, and atypical lipomatous tumors.

Biology and Management of Deep-seated Atypical Lipomatous Tumor of the Extremities

Adipocytic neoplasms are frequently encountered in clinical practice. Atypical lipomatous tumor (ALT) is a locally aggressive but non-metastasizing adipocytic neoplasm that primarily occurs in the proximal extremities of middle-aged to older adults. Histologically, ALT is divided into adipocytic (lipoma-like), sclerosing and inflammatory subtypes. The sclerosing subtype is an unfavorable prognostic factor for local recurrence. ALT is characterized by supernumerary ring and/or giant rod chromosomes. These rings and giant markers invariably contain amplified sequences originating from the long arm of chromosome 12, including the MDM2 proto-oncogene (MDM2) and cyclin-dependent kinase 4 (CDK4) gene. MDM2 and/or CDK4 nuclear immunopositivity is present in most cases. Confidently differentiating deep-seated ALT from deep-seated ordinary lipoma is often difficult on imaging. Moreover, the sclerosing subtype may mimic a higher grade liposarcoma. Detection of MDM2 amplification by fluorescence in situ hybridization would be helpful diagnostically for ALT in more difficult cases. The standard treatment for deep-seated ALT is surgery. Although there is no consensus on the best surgical approach for deep-seated ALT of the extremities, the use of marginal resection is acceptable to preserve musculoskeletal function. This review provides an overview of the current knowledge on the clinical and imaging characteristics, pathogenesis, histopathology, and management of deep-seated ALT of the extremities.

Lipoblastoma-Like Tumor and Fibrosarcoma-Like Lipomatous Neoplasm Represent the Same Entity: A Clinicopathologic and Molecular Genetic Study of 23 Cases Occurring in Both Men and Women at Diverse Locations

Lipoblastoma-like tumor (LLT) is a benign soft tissue tumor demonstrating mixed morphologic features of lipoblastoma, myxoid liposarcoma, and spindle cell lipoma but lacking genetic alterations associated with those tumors. LLT was originally thought to be specific to the vulva but has since been reported in the paratesticular region. The morphologic features of LLT overlap with those of "fibrosarcoma-like lipomatous neoplasm" (FLLN), a rare, indolent adipocytic neoplasm considered by some to form part of the spectrum of atypical spindle cell and pleomorphic lipomatous tumor. We compared the morphologic, immunohistochemical, and genetic features of 23 tumors previously classified as LLT (n = 17) and FLLN (n = 6). The 23 tumors occurred in 13 women and 10 men (mean age, 42 years; range, 17 to 80 years). Eighteen (78%) cases arose in the inguinogenital region, whereas 5 tumors (22%) involved noninguinogenital soft tissue, including the flank (n = 1), shoulder (n = 1), foot (n = 1), forearm (n = 1), and chest wall (n = 1). Microscopically, the tumors were lobulated and septated, with variably collagenized fibromyxoid stroma, prominent thin-walled vessels, scattered univacuolated or bivacuolated lipoblasts, and a minor component of mature adipose tissue. Using immunohistochemistry, 5 tumors (42%) showed complete RB1 loss, with partial loss in 7 cases (58%). RNA sequencing, chromosomal microarray, and DNA next-generation sequencing study results were negative for significant alterations. There were no clinical, morphologic, immunohistochemical, or molecular genetic differences between cases previously classified as LLT or FLLN. Clinical follow-up (11 patients [48%]; range, 2-276 months; mean, 48.2 months) showed all patients were alive without disease, and only one patient had experienced a single local recurrence. We conclude that LLT and FLLN represent the same entity, for which "LLT" seems most appropriate. LLT may occur in either sex and any superficial soft tissue location. Careful morphologic study and appropriate ancillary testing should allow for the distinction of LLT from its potential mimics.

PRDM10 RCC: A Birt-Hogg-Dubé-like Syndrome Associated With Lipoma and Highly Penetrant, Aggressive Renal Tumors Morphologically Resembling Type 2 Papillary Renal Cell Carcinoma

OBJECTIVE

To characterize the clinical manifestations and genetic basis of a familial cancer syndrome in patients with lipomas and Birt-Hogg-Dubé-like clinical manifestations including fibrofolliculomas and trichodiscomas and kidney cancer.

METHODS

Genomic analysis of blood and renal tumor DNA was performed. Inheritance pattern, phenotypic manifestations, and clinical and surgical management were documented. Cutaneous, subcutaneous, and renal tumor pathologic features were characterized.

RESULTS

Affected individuals were found to be at risk for a highly penetrant and lethal form of bilateral, multifocal papillary renal cell carcinoma. Whole genome sequencing identified a germline pathogenic variant in PRDM10 (c.2029 T>C, p.Cys677Arg), which cosegregated with disease. PRDM10 loss of heterozygosity was identified in kidney tumors. PRDM10 was predicted to abrogate expression of FLCN, a transcriptional target of PRDM10, which was confirmed by tumor expression of GPNMB, a TFE3/TFEB target and downstream biomarker of FLCN loss. In addition, a sporadic papillary RCC from the TCGA cohort was identified with a somatic PRDM10 mutation.

CONCLUSION

We identified a germline PRDM10 pathogenic variant in association with a highly penetrant, aggressive form of familial papillary RCC, lipomas, and fibrofolliculomas/trichodiscomas. PRDM10 loss of heterozygosity and elevated GPNMB expression in renal tumors indicate that PRDM10 alteration leads to reduced FLCN expression, driving TFE3-induced tumor formation. These findings suggest that individuals with Birt-Hogg-Dubé-like manifestations and subcutaneous lipomas, but without a germline pathogenic FLCN variant, should be screened for germline PRDM10 variants. Importantly, kidney tumors identified in patients with a pathogenic PRDM10 variant should be managed with surgical resection instead of active surveillance.

Silver In Situ Hybridization for the Rapid Assessment of MDM2 Amplification in Soft Tissue and Bone Tumors. Validation Based on an Audit of 192 Consecutive Cases Evaluated by Silver In Situ Hybridization and Fluorescence In Situ Hybridization

The discovery of almost invariable mouse double minute 2 (MDM2) amplification among atypical lipomatous tumors (ALT)/well-differentiated liposarcoma and dedifferentiated liposarcoma is incorporated into the contemporary diagnostic workup of fatty lesions. MDM2 amplifications are also found frequently in intimal sarcomas and in low-grade osteogenic sarcoma. At present, fluorescence in situ hybridization (FISH) is the reference test for MDM2 assessment. We are interested in evaluating silver in situ hybridization (SISH) for this purpose. Between October 2016 and May 2020, in 192 consecutive cases requiring MDM2 FISH, SISH was also performed concurrently, including 77 (40.1%) core biopsies and 115 (58.9%) surgical specimens. The mean patient age was 61.0 years. SISH results were available overnight or within 48 hours if repeat testing was required. FISH results were available within 2 to 5 weeks. The cost of SISH was one third of FISH. FISH demonstrated MDM2 amplification in 44 cases (23.6%), was negative in 144 cases (74.4%) and nondiagnostic in 4 decalcified cases (2.0%). SISH showed MDM2 amplification in 33 cases (17.2%), no amplification in 119 cases (62.0%), and indeterminate results because of poor signal in 40 (20.8%) cases. All 33 (100%) SISH-amplified tumors and 113 of 119 (95.0%) nonamplified results were confirmed by FISH. There were no clear differences in the performance of SISH on NCB versus surgical specimens. The overall performance indices of SISH are sensitivity 75%, specificity 78.5%, positive predictive value 100%, and negative predictive value 95.8%. FISH is not required when SISH is clearly amplified. This is clinically useful and improves efficiency. Nonamplified SISH results provide early indications of the likely FISH findings, but there is a 4.2% chance of FISH being positive. At present, the main drawback of SISH is the high rate of nondiagnostic tests. Optimization of SISH signal detection to reduce the proportion of indeterminate results is our current focus.

[Fat-forming solitary fibrous tumor with NAB2/ STAT6 gene fusion. Case report of genial location and literature review]

The lipomatous variety solitary fibrous tumor is a soft tissue neoplasm composed of mature adipose tissue and hemangiopericytoma areas. A 53-year-old man consulted for facial asymmetry and maxillofacial magnetic resonance imaging showed a cystic lesion, 3 x 2 cm in size, in front of the anterior wall of the maxillary sinus. Histologically, there were dense spindle cells expressing CD34, CD99, Bcl-2, and STAT6, myxoid zones, hemangiopericytomatous blood vessels, and S100 positive adipocytes. NAB2/STAT6 gene fusion was revealed by RT-PCR. The main differential diagnosis was raised with the spindle cell lipoma and malignant variant of the lipomatous solitary fibrous tumor. STAT6 overexpression and NAB2/STAT6 gene fusion are specific for lipomatous solitary fibrous tumor and the presence of lipoblasts and atypical lipomatous tumor areas suggests malignancy. These tumors located in the head and neck region have a benign biological behavior.

Transcutaneous electrical stimulation therapy and genetic analysis in Dercum's disease: A pilot study

Dercum's disease (DD), or adiposis dolorosa, is a rare condition of unknown etiology characterized by growth of painful subcutaneous adipose tissue. No specific treatment exists. Pain is often invalidating and resistant to analgesic drugs. We tested the efficacy of Frequency Rhythmic Electrical Modulation System (FREMS) therapy on pain relief. Subcutaneous biopsies were performed for genetic analysis.Nine DD patients were enrolled. Five cycles of FREMS at 3-month intervals during 1 year were administered. Visual analogue scale (VAS), Bartel Index Questionnaire and Short Form 36 questionnaire were used to measure pain and general health status at baseline, 6 and 12 months. Dual-energy X-ray absorptiometry (DEXA) quantified fat mass. Next-Generation Sequencing (NGS) was performed on adipose tissue biopsies and peripheral blood sample to search for somatic variants and specific protein pathway mutation.Seven patients were included in the final analysis. FREMS induced a reduction in VAS score (from 92 to 52.5, P = .0597) and a significant improvement in SF-36 domains (Physical functioning, Role limitation due to physical health, Body pain, Vitality, Social functioning, P < .05). No modification in anthropometrics and DEXA values was observed. The analysis of the mitochondrial Displacement loop (D-loop) region confirmed the clonality of all lipomatous lesions. The presence of the mitochondrially encoded tRNA-Lysine (MT-TK) m.8344A>G variant, occasionally identified in patients with multiple symmetric lipomatosis, was excluded in all subjects. On the other hand, we observed variants in genes belonging to signaling pathways involved in cell cycle and proliferation (Phosphoinositide 3-kinase/AKT/mTOR, MAPK/ERK, and Hippo).FREMS can be a useful tool to alleviate pain and improve overall quality of life in patients with DD. Genetic analysis highlighted the molecular heterogeneity of lipomas.

Diagnostic Utility Of Fish For MDM2 In Adipocytic Neoplasms

BACKGROUND

The 2013 World Health Organization (WHO) classification of soft tissue and bone tumours recognizes benign entities such as lipoma and four major liposarcoma subtypes: atypical lipomatous tumour/well differentiated liposarcomas (ALT/WDL), dedifferentiated liposarcomas (DDL), myxoid liposarcoma and pleomorphic liposarcoma. This classification of atypical and malignant adipocytic tumours has evolved significantly over the past few decades owing to contributions from cytogenetics, molecular genetics and Immunohistochemical correlates. Most ALT/WDLs can be diagnosed on histology; however, some of the biopsies may be underdiagnosed due to focal atypia or limited nature of tissue for the biopsy. Fluorescence in situ hybridization (FISH) for MDM2 (located at 12q14-15) gene amplification has emerged as gold standard for diagnosis in cases with limiting histological factors.

METHODS

We studied MDM2 amplification by FISH in 55 such problematic adipocytic tumours with overlapping morphological features and a retrospective analysis was made against their corresponding histological features.

RESULTS

MDM2 amplification correctly identified 11 of 17 ALT/WDLs (64.71% concordance) and 8 of 10 Lipomas (80% concordance). We were able to differentiate liposarcomas from other high grade sarcomatous lesions and sub-classified these lesions into pleomorphic and dedifferentiated types.

CONCLUSIONS

FISH for MDM2 amplification should be used as a gold standard in adjunction with morphology and immunohistochemistry for problematic adipocytic neoplasms.

Multiple endocrine neoplasia type 1 with a frameshift mutation in its gene accompanied by a giant cervical lipoma and multiple fatty deposits in the pancreas: case report

BACKGROUND

Multiple endocrine neoplasia type 1 (MEN1) is a syndrome characterized by pituitary neoplasia, primary hyperparathyroidism and pancreatic endocrine tumor. Here we show a case of MEN1 with a germline frameshift mutation in its gene accompanied by a giant cervical lipoma and multiple fatty deposits in the pancreas.

CASE PRESENTATION

A 28-year-old man noticed the decreased visual acuity of both eyes and visited our institution. Since he was diagnosed as visual disturbance and brain computer tomography (CT) showed a mass in the pituitary fossa, he was hospitalized in our institution. Endoscopic trans-sphenoidal hypophysectomy and total parathyroidectomy with auto-transplantation were performed, and a giant cervical lipoma was resected. Furthermore, in genetic search, we found a germline frameshift mutation in MEN1 gene leading to the appearance of a new stop codon.

CONCLUSIONS

We should bear in m ind that giant skin lipoma and multiple abnormal fatty deposits in the pancreas could be complicated with MEN1.

Overgrowth syndromes and new therapies

Overgrowth syndromes represent a diverse group of disorders with overlapping features. Interdisciplinary management by a team of experts in vascular anomalies is crucial for establishing the correct diagnosis and optimizing outcomes for these patients. Unique management considerations include increased risk for thrombosis and in some cases, cancer. In recent years, research has demonstrated that these disorders are primarily caused by somatic mutations in growth pathways, particularly the PI3K-mTOR pathway. This improved understanding had led to promising new therapies for this group of patients.

Dysplastic lipoma: potential diagnostic pitfall of using MDM2 RNA in situ hybridization to distinguish between lipoma and atypical lipomatous tumor

The distinction between lipoma and atypical lipomatous tumor can be challenging in some cases. While detection of MDM2 gene amplification via fluorescence in situ hybridization (FISH) has been well established as a diagnostic tool to distinguish atypical lipomatous tumor and well-differentiated liposarcoma from benign mimics, MDM2 RNA in situ hybridization (RNA-ISH) has recently been proposed as an alternative diagnostic assay. During clinical workup for lipomatous tumors using MDM2 RNA-ISH, we noticed several dysplastic lipomas that were positive for MDM2 RNA-ISH but negative for MDM2 amplification by FISH. In this study, we examined a series of 11 dysplastic lipomas, all confirmed to be negative for MDM2 amplification by FISH. Positive MDM2 RNA-ISH was noted in 10 (91%) dysplastic lipomas. Single-nucleotide polymorphism array on one dysplastic lipoma identified the presence of homozygous deletion of 13q, including the RB1 gene locus with no evidence of MDM2 copy number gain. Our findings on the discordance between MDM2 FISH and MDM2 RNA-ISH highlight the potential utility and pitfalls of using MDM2 RNA-ISH in the distinction of atypical lipomatous tumor and related liposarcomas from dysplastic lipoma.

Atypical Lipomatous Tumor/Well-Differentiated Liposarcoma With Features Mimicking Spindle Cell Lipoma

Atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDL) and spindle cell lipoma are lipomatous tumors with distinct clinical, molecular, and prognostic features. Although histological and immunophenotypic features can overlap between ALT/WDL and spindle cell lipoma, the oncogenesis and clinical behavior are markedly different. In borderline cases, molecular analysis for MDM2 or CDK4 amplification can aid in distinguishing ALT/WDL from spindle cell lipoma. Although dedifferentiated liposarcoma has been reported to harbor both MDM2 amplification and loss of the RB1 region, we are not aware of a reported RB1 loss in well-differentiated ALT/WDL. In this article, we present a 69-year-old woman with a lipomatous tumor in the gluteal region that histologically, immunohistochemically, and molecularly mimicked spindle cell lipoma (with positive immunohistochemical staining for CD34 and loss of the RB1 gene region), yet harbored amplification of MDM2 and CDK4 confirmed by fluorescence in situ hybridization, supporting classification as ALT/WDL. This case strengthens the argument that in atypical clinical contexts, molecular studies for MDM2/CDK4 should be considered in tumors resembling spindle cell lipoma.

Identification of somatic alterations in lipoma using whole exome sequencing

Lipomas are benign fatty tumors with a high prevalence rate, mostly found in adults but have a good prognosis. Until now, reason for lipoma occurrence not been identified. We performed whole exome sequencing to define the mutational spectrum in ten lipoma patients along with their matching control samples. We presented genomic insight into the development of lipomas, the most common benign tumor of soft tissue. Our analysis identified 412 somatic variants including missense mutations, splice site variants, frameshift indels, and stop gain/lost. Copy number variation analysis highlighted minor aberrations in patients. Kinase genes and transcriptions factors were among the validated mutated genes critical for cell proliferation and survival. Pathway analysis revealed enrichment of calcium, Wnt and phospholipase D signaling in patients. In conclusion, whole exome sequencing in lipomas identified mutations in genes with a possible role in development and progression of lipomas.

Exome sequencing identifies a de novo frameshift mutation in the imprinted gene ZDBF2 in a sporadic patient with Nasopalpebral Lipoma-coloboma syndrome

Nasopalpebral lipoma-coloboma syndrome (NPLCS, OMIM%167730) is an uncommon malformation entity with autosomal dominant inheritance characterized by the combination of nasopalpebral lipoma, colobomas in upper and lower eyelids, telecanthus, and maxillary hypoplasia. To date, no genetic defects have been associated with familial or sporadic NPLCS cases and the etiology of the disease remains unknown. In this work, the results of whole exome sequencing in a sporadic NPLCS patient are presented. Exome sequencing identified a de novo heterozygous frameshift dinucleotide insertion c.6245_6246 insTT (p.His2082fs*67) in ZDBF2 (zinc finger, DBF-type containing 2), a gene located at 2q33.3. This variant was absent in parental DNA, in a set of 300 ethnically matched controls, and in public exome variant databases. This is the first genetic variant identified in a NPLCS patient and evidence supporting the pathogenicity of the identified mutation is discussed. © 2016 Wiley Periodicals, Inc.

Rb1 and Pten Co-Deletion in Osteoblast Precursor Cells Causes Rapid Lipoma Formation in Mice

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.

Characterization of the 12q amplicons in lipomatous soft tissue tumors by multiplex ligation-dependent probe amplification-based copy number analysis

BACKGROUND/AIM

Well-differentiated liposarcoma (WDLPS) and de-differentiated liposarcoma (DDLPS) are characterized by amplified sequences derived from the long arm of chromosome 12. The goal of the present study was to identify, besides the well-known candidate genes, novel relevant genes in these large, complex 12q amplicons.

MATERIALS AND METHODS

Using multiplex ligation-dependent probe amplification, genetic alterations in 19 different genes of 12q12-24 were evaluated in 77 lipomatous soft tissue tumors (including lipomas, WDLPS, DDLPS and pleomorphic liposarcomas).

RESULTS

We recorded several amplified genes of 12q13-15, including miR-26a-2, a gene not well studied in liposarcoma, and the well-known and previously described genes murine double minute 2 (MDM2), YEATS domain-containing protein 4 (YEATS4), high-mobility AT-hook 2 (HMGA2), cyclin-dependent kinase 4 (CDK4) and tetraspanin 31 (TSPAN31). Interestingly, the amplification profiles of these six genes were found to be significantly different between WDLPS and DDLPS, more frequently having a high-level status in DDLPS than in WDLPS. In addition, DDLPS were found to have significantly higher mean amplification ratios compared to WDLPS. Moreover, we identified additional genes exclusively amplified in DDLPS in 12q13, 12q21 and 12q24, including glioma-associated oncogene homolog 1 (GLI1), mitogen activated protein kinase kinase kinase 12 (MAP3K12), cyclin-dependent kinase 2 (CDK2), ALX homeobox 1 (ALX1) and T-box 5 (TBX5).

CONCLUSION

Differences in amplification profiles among WDLPS and DDLPS may be related to progression/de-differentiation in liposarcomas and show how in the future amplification profiles could provide an adjunctive tool in characterizing progression to DDLPS. In addition, we identified additional genes exclusively amplified in DDLPS, which may play a role in liposarcomagenesis, particularly in the de-differentiation process.

Atypical lipomatous tumor with structural rearrangements involving chromosomes 3 and 8

Atypical lipomatous tumor (ALT) is an intermediate (locally aggressive) mesenchymal neoplasm with the potential to dedifferentiate to higher grades over time. It is cytogenetically characterized by the presence of one or more supernumerary ring and giant marker chromosomes. These abnormal chromosomes invariably contain amplified sequences derived from the 12q14-15 region. We describe a unique cytogenetic finding of ALT arising in the right lower back of a 42-year-old man. Magnetic resonance imaging demonstrated a predominantly fatty mass with irregularly thickened, linear, swirled, and nodular septa. Contrast-enhanced fat-suppressed T1-weighted images showed significant enhancement of the non-adipose areas. A sub-extensive resection was performed. Histologically, the tumor consisted predominantly of mature fat cells with atypical stromal cells and multivacuolated lipoblasts. Immunohistochemically, the tumor cells were positive for p16 (diffuse and strong signal) and cyclin-dependent kinase-4 (focal and weak signal) but negative for murine double-minute 2. Cytogenetic analysis displayed a t(3;8)(q28;q13) translocation as the sole anomaly or concomitant with a few other numerical and structural alterations. There has been no evidence of local recurrence two months after surgery. To the best of our knowledge, this is the first case of ALT with structural aberrations involving chromosomes 3 and 8, associated with an absence of 12q rearrangements.

Cloves syndrome: a case report and perinatal diagnostic findings

We report a neonate with prenatal ultrasound imaging features suggestive of CLOVES syndrome, confirmed postnatally by clinical and imaging findings of the constellation of truncal overgrowth, cutaneous capillary malformations, lymphatic and musculoskeletal anomalies. The clinical, radiological and histopathological findings noted in our patient help differentiate from other overgrowth syndromes such as Proteus syndrome. We report perinatal findings and add new clinical findings of this rare syndrome.

Case report of an oral fibroma occurring in a patient with familial multiple lipomas

A wide variety of lesions may manifest in the oral soft tissues that could be confusing and challenging for the clinicians. These lesions could be as simple as trauma-induced ulcers that need about 2 weeks to heal, to a more complicated situation such as oral cancer. The key points in developing diagnosis and a possible treatment plan may include a comprehensive oral examination, simple understanding of normal oral tissue features, and knowledge of common oral lesions. This will help in the development of a differential diagnosis of the oral lesions/masses based on the risk factors in that particular patient. In this case report, we present a simple oral mass in a patient who had an oral fibroma and lipomas in other areas.

Utility of fluorescence in situ hybridization to detect MDM2 amplification in liposarcomas and their morphological mimics

The atypical lipomatous tumor (ALT)/well-differentiated liposarcoma (WDLS) and the de-differentiated liposarcoma (DDLS) represent the most common category of liposarcomas. ALT/WDLSs and DDLSs are often difficult to distinguish from other tumors with similar morphological characteristics. In this study, we investigated whether the detection of amplified or overexpressed murine double-minute 2 (MDM2) can be a useful diagnostic ancillary aid. We used fluorescent in situ hybridization (FISH) and immunohistochemistry (IHC) to detect MDM2 amplification and protein overexpression, respectively, in 49 WDLSs, 5 DDLSs, 23 myxoid liposarcomas, 25 benign lipomatous tumors, and 75 spindle and pleomorphic sarcomas. MDM2 amplification was detected in 48 of 49 WDLSs, 5 of 5 DDLSs, 2 of 9 malignant peripheral nerve sheath tumors, and 2 of 10 myxofibrosarcomas. We did not detect MDM2 amplification in any of the benign lipomatous tumors. FISH-mediated detection of MDM2 amplification was the most valuable diagnostic aid for ALT/WDLS, as determined by using the Fisher exact test to compare two different diagnoses of 19 biopsies. On the contrary, unequivocal nuclear overexpression of MDM2 was found in only 10 of 50 ALT/WDLSs. The sensitivity and specificity of MDM2 amplification in distinguishing a DDLS from spindle and pleomorphic sarcomas were 100% and 95%, respectively, while those of MDM2 overexpression were 100% and 87%, respectively. In conclusion, our results indicate that FISH-mediated detection of MDM2 amplification is the most useful adjunct in the diagnosis of both ALT/WDLS and DDLS. However, IHC-mediated detection of MDM2 protein is useful only for the diagnosis of DDLS.

Rearrangement of HMGA2 in a case of infantile lipoblastoma without Plag1 alteration

Lipoblastoma is a rare benign adipocytic tumor that occurs usually in children. It can be difficult to distinguish a lipoblastoma from other lipogenic tumors. In such cases, the detection of a rearrangement of the PLAG1 gene by fluorescence in situ hybridization analysis is useful for characterizing a lipoblastoma. We present here a novel case of morphological infantile lipoblastoma showing a rearrangement of HMGA2 instead of the classical PLAG1 alteration. HMGA2 is the main target of clonal aberrations encountered in lipomas. This result supports the hypothesis that benign lipomatous tumors harboring PLAG1 or HMGA2 rearrangement could constitute a unique pathogenetic entity.

[Lipoblastoma and lipoblastomatosis: especially in children]

Lipoblastoma and lipoblastomatosis are rare benign fatty tumours that mainly occur in children under the age of 3 years. Several body sites can be affected. The term 'lipoblastoma' is reserved for an encapsulated neoplasm; 'lipoblastomatosis' for tumours demonstrating infiltrative growth. Most of the clinical symptoms arise from a mass effect of the tumour on surrounding tissues. The tumours should be differentiated from lipoma, myxoid liposarcoma and hibernoma. A clear distinction can be made by cytogenetic analysis, since each of these tumours is known for its own typical genetic abnormalities. In lipoblastoma and lipoblastomatosis, these include a breakpoint in the 8q11-13 region or polysomy of chromosome 8, both leading to the activation of the oncogenic pleomorphic adenoma gene 1 (PLAG1) on 8q12. Treatment consists of surgical resection; there is no need for radiotherapy or chemotherapy. Clinical outcome depends on the completeness of the resection and damage that is done to the surrounding tissues during surgery.

Specificity of fusion genes in adipocytic tumors

BACKGROUND

In subsets of adipocytic tumors, specific chromosomal translocations lead to the generation of fusion genes. The high mobility group A2 (HMGA2)-lipoma preferred partner (LPP) and the reciprocal LPP-HMGA2 represent such fusion genes in lipoma, while the human translocation liposarcoma (TLS)-CCAAT/enhancer binding protein (C/EBP) homologous protein (CHOP) and the Ewing sarcoma (EWS)-CHOP in liposarcoma. However, the specificity of these fusion genes has not been established in a variety of adipocytic tumors.

PATIENTS AND METHODS

One hundred and seventy-two cases of adipocytic tumors, comprising 98 cases of lipoma and 74 cases of liposarcoma, were analyzed for the possible expression of HMGA2-LPP, LPP-HMGA2, TLS-CHOP and EWS-CHOP fusion genes, using a reverse-transcription polymerase chain reaction method.

RESULTS

In lipoma, twenty-two cases (22.4%) were associated with either HMGA2-LPP or LPP-HMGA2, while neither TLS-CHOP nor EWS-CHOP transcript was detectable. On the contrary, in liposarcoma, neither HMGA2-LPP nor LPP-HMGA2 transcript was detectable, although twenty-five cases (33.8%) were related to either TLS-CHOP or EWS-CHOP.

CONCLUSION

HMGA2-LPP and LPP-HMGA2 were specific to lipoma, and TLS-CHOP and EWS-CHOP were specific to liposarcoma.

Expression of HMGA2-LPP and LPP-HMGA2 fusion genes in lipoma: identification of a novel type of LPP-HMGA2 transcript in four cases

BACKGROUND

In a subset of lipoma, a specific t(3;12)(q27-28;q14-15) chromosomal translocation leads to the fusion of the high mobility group A2 (HMGA2) gene and the lipoma preferred partner (LPP) gene. Although the expression of HMGA2-LPP fusion gene has been reported in lipomas, the reciprocal LPP-HMGA2 fusion gene has rarely been described.

MATERIALS AND METHODS

Ninety-eight cases of lipoma were analyzed for the possible expression of HMGA2-LPP and LPP-HMGA2 fusion genes using a reverse-transcription polymerase chain reaction method.

RESULTS

Ten lipomas (10%) revealed both HMGA2-LPP and LPP-HMGA2 fusion transcripts, nine (9%) only HMGA2-LPP, and three (3%) only LPP-HMGA2. DNA sequencing analysis demonstrated that the HMGA2-LPP transcript in 19 lipomas consisted of exons 1-3 of HMGA2 and exons 9-11 of LPP, which was described previously. Out of 13 lipomas with LPP-HMGA2 transcript, 9 were associated with a previously reported LPP-HMGA2 fusion transcript, which fuses exon 8 of LPP to exon 4 of HMGA2, while 4 with a novel type of LPP-HMGA2 fusion transcript, which fuses exon 7 of LPP to exon 4 of HMGA2.

CONCLUSION

In addition to the HMGA2-LPP fusion gene, the LPP-HMGA2 fusion gene could have some specific roles for lipomagenesis. The biological implications of the expression and the variation of LPP-HMGA2 fusion transcripts need to be elucidated.

A syndrome with painful lipomas, familial dysarthria, abnormal eye-movements and clumsiness

A syndrome of dysarthria, clumsiness and abnormal ocular movements are described in a man and his 3 children. His father, who died when our patient was born, also had the same speech abnormality. Our patient also had multiple painful lipomas suggesting a probable diagnosis of adipositas dolorosa Dercum. Although he looked muscular he complained of muscular weakness and fatigue. Oral treatment with a local anesthetic, mexiletin, inhibited the pain in the lipomas. Analysis of the speech disorder in our patient and his children revealed disturbances in the coordination of jaws, larynx and tongue with a poor control of pitch and volume and impaired intelligibility. The poor fine coordination of hands, clumsiness when walking, dysarthria and disturbance of eye-movements could be due to a familial malformation in the pons or cerebellum. Computer tomography and X-ray of head were normal but the grooves on the surface of the cerebellum were more marked than usual.

Clinicopathological features of lipomas with gene fusions involving HMGA2

BACKGROUND

Despite accumulating knowledge of chimeric genes derived from fusion of the HMGA2 gene with multiple partners in lipomas, the different clinicopathological features of lipomas depending on different gene aberrations have not been well documented. The purpose of this study was to examine the clinical significance of the expression of fusion genes in lipomas.

PATIENTS AND METHODS

The expressions of three previously reported gene fusion transcripts, including HMGA2/LPP, HMGA2/RDC1 and HMGA2/NFIB, were analyzed in 102 tumors from patients with lipomas.

RESULTS

There were 23 cases (22.5%) expressing HMGA2/LPP, 2 cases (1.9%) expressing HMGA2/RDC1 and no cases of HMGA2/NFIB expression (0%). There were no significant intergroup differences in age, gender, body mass index, tumor size or location. The magnetic resonance images and pathological features were also not different in regard to the status of fusion gene expression.

CONCLUSION

There were no significant differences of clinicopathological features in patients with lipoma with or without these fusion gene transcripts.

Cervical lipoblastoma: Case report, review of literature, and genetic analysis

BACKGROUND

Lipoblastoma is a rare, benign tumor of infants and children, usually occurring in the extremities and trunk, with only a few cases reported in the neck.

METHODS

We describe the case of an infant with a rapidly enlarging, painless neck mass. MRI revealed a 4-cm-diameter mass deep to the paraspinal muscles, in close proximity to the C2 vertebral foramen. Review of literature, diagnostic methods, and genetics of lipomatous tumors are discussed.

RESULTS

Complete surgical excision via a posterior cervical approach demonstrated irregular lobules of immature fat cells separated by a loose, myxoid connective tissue. Histology and genetic analysis confirmed the diagnosis of lipoblastoma.

CONCLUSION

Cervical lipoblastoma is rare, and typically presents as an asymptomatic, painless mass, rarely causing airway obstruction or nerve compression. MRI can be helpful in identifying the lipomatous nature of the mass, but the findings can be inconsistent due to variable maturity of fat cells and the mesenchymal content of the tumor. Chromosomal analysis is useful in differentiating lipoblastoma from liposarcoma. Recommended treatment is complete surgical excision.

Detection of MDM2-CDK4 Amplification by Fluorescence In Situ Hybridization in 200 Paraffin-embedded Tumor Samples: Utility in Diagnosing Adipocytic Lesions and Comparison With Immunohistochemistry and Real-time PCR

Atypical lipomatous tumor/well-differentiated liposarcomas and dedifferentiated liposarcomas are characterized by the amplification of MDM2 and CDK4 genes. To evaluate the accuracy of fluorescence in situ hybridization (FISH) analysis in the differential diagnosis of adipose tissue tumors, we investigated MDM2-CDK4 status by FISH, real-time polymerase chain reaction (PCR) [quantitative PCR (Q-PCR)] and immunohistochemistry (IHC) in a series of 200 adipose tumors. First, we evaluated MDM2-CDK4 amplification and expression in a series of 94 well-defined adipose tissue tumors. Results showed that FISH was interpretable in 45 of 50 cases (90%), and was more specific and sensitive than Q-PCR and IHC. We then used the same techniques as complementary diagnostic tools in a series of 106 adipose and soft tissue tumors of unclear diagnosis to distinguish between (i) lipomas and atypical lipomatous tumor/well-differentiated liposarcomas, (ii) malignant undifferentiated tumors and dedifferentiated liposarcomas, and (iii) a variety of benign tumors and liposarcomas. Our results indicate that although helpful, IHC alone is often insufficient to solve diagnostic problems. FISH and Q-PCR methods gave concordant results and were equally informative in most cases. However, the proportion of noninterpretable cases was slightly higher with FISH than with Q-PCR. When tumor cells represented a minor component of the tumor tissue, such as with inflammatory tumors, FISH was more powerful than Q-PCR by allowing visualization of individual cells. In conclusion, we recommend that the evaluation of MDM2-CDK4 amplification using FISH or Q-PCR be used to supplement IHC analysis when diagnosis of adipose tissue tumors is not possible based on clinical and histologic information alone.

Gains and complex rearrangements of the 12q13-15 chromosomal region in ordinary lipomas: the "missing link" between lipomas and liposarcomas?

Well-differentiated liposarcomas (WDLPS) classically contain high-level amplification of 12q14-15 sequences, including the MDM2 and CDK4 genes, while lipomas are characterized by simple structural chromosome aberrations often involving HMGA2 at 12q15. Previous studies have shown that low-level gain of the 12q14-15 region, such as trisomy 12 and 12q15-24 duplication, might be sufficient for the development of minimal atypia and formation of WDLPS. Moreover, because some features, such as overexpression of HMGA2, are shared by both lipomas and WDLPS, it has been hypothesized that lipomas and WDLPS may form a genetic and morphological continuum. We report here the results of molecular cytogenetic analysis of 8 lipomas that had unusual chromosomal features resulting in gains of 12q14-15. While 3 cases had simple numerical rearrangements (trisomy 12) or structural rearrangements (unbalanced translocations with 12q gains), 5 cases were particularly intriguing because of peculiar features such as giant chromosomes, supernumerary chromosomes or neocentromeres that usually are the hallmark of WDLPS. Gain of 12q14-15 sequences including extra copies of MDM2 and CDK4 were detected by fluorescence in situ hybridization analysis in all analyzed cases but no expression of MDM2 and CDK4 was observed suggesting that these genomic imbalances had no functional consequence. We observed rearrangements of HMGA2 in 5 out 8 cases. Altogether, our results indicate that moderate gains of 12q are not always associated with a malignant phenotype, and that some intermediary forms exist between classical lipomas and classical WDLPS. Some of these intermediary forms may correspond to a genomic premalignant condition while some may have no malignant potential.

Adult obstructive sleep apnea related to nasopharyngeal obstruction: a case of retropharyngeal lipoma and pathogenetic considerations

Cervico facial lipomas are relatively rare and only a few of them affect retropharyngeal space. Because of their slow growth rate, they can reach large size before causing respiratory disturbances and surgery is the treatment of choice. We present a case of 73-year-old female patient with severe obstructive sleep apnea [Apnea Hypopnea Index (AHI) = 43; mean SaO2 = 84%; lowest SaO2 = 60%; time of sleep with SaO2<90% = 35%]. Computed tomography scan showed a low attenuation bilobed retropharyngeal mass (5 x 2 x 2.5 cm) compatible with lipoma, extending from the nasopharynx to the superior bound of the oropharynx (at the level of C2-C3 passage). Removal of the tumor cured the obstructive sleep apnea; the sleep study at 1 month follow-up showed the normalization of the somnographic parameters (AHI = 12; lowest SaO2 = 76%; mean SaO2 = 95%; time of sleep with SaO2<90% = 4%).

Does parosteal liposarcoma differ from other atypical lipomatous tumors/well-differentiated liposarcomas? A molecular cytogenetic study using combined multicolor COBRA-FISH karyotyping and array-based comparative genomic hybridization

Parosteal adipocytic tumors of the bone are extremely rare. As a result, (cyto-) genetic data on this entity are essentially lacking. In the literature there is debate as to whether these lesions should be classified according to the criteria used in soft-tissue tumor pathology, or if they should be considered a separate bone tumor entity. Here we present a 68-year-old male patient with a tumor in his right upper leg diagnosed as parosteal atypical lipomatous tumor/well-differentiated liposarcoma (ALT/WDLS) on the basis of clinico-radiologic and pathologic findings. Molecular cytogenetic investigations using combined binary ratio labeling fluorescence in situ hybridization and array comparative genomic hybridization showed abnormalities, which are in accordance with the histologic appearance of an atypical lipomatous tumor/well-differentiated liposarcoma. Therefore, on the basis of these molecular cytogenetic investigations, we conclude that parosteal liposarcoma is not a separate entity but should be categorized within the spectrum of soft-tissue ALT/WDLS.

Assessment of the clinical and molecular impact of different cytogenetic subgroups in a series of 272 lipomas with abnormal karyotype

Conventional lipomas harbor karyotypic changes that could be subdivided into four, usually mutually exclusive, categories: rearrangement, in particular through translocations, of chromosome bands 12q13-15, resulting in deregulation of the HMGA2 gene, loss of material from or rearrangement of chromosome 13, supernumerary ring or giant marker chromosomes, and aberrations of chromosome band 6p21. In the present study, 272 conventional lipomas, two-thirds of them deep-seated, with acquired clonal chromosome changes were assessed with regard to karyotypic and clinical features. A nonrandom distribution of breakpoints and imbalances could be confirmed, with 83% of the cases harboring one or more of the previously known cytogenetic hallmarks. Correlation with clinical features revealed that lipomas with rings/giant markers were larger, occurred in older patients, were more often deep-seated, and seemed to have an increased tendency to recur locally, compared with tumors with other chromosome aberrations. The possible involvement of the HMGA2 gene in cases that did not show any of the characteristic cytogenetic changes was further evaluated by locus-specific metaphase fluorescence in situ hybridization (FISH) and RT-PCR, revealing infrequent cryptic disruption of the gene but abundant expression of full length or truncated transcripts. By FISH, we could also show that breakpoints in bands 10q22-23 do not affect the MYST4 gene, whereas breakpoints in 6p21 or 8q11-12 occasionally target the HMGA1 or PLAG1 genes, respectively, also in conventional lipomas.

Pulmonary lipomatous hemangiopericytoma: report of a rare tumor and comparison with solitary fibrous tumor

Lipomatous hemangiopericytoma is a rare mesenchymal tumor showing areas of lipid-containing cells admixed with a spindle-cell component. Like other hemangiopericytomas, it shows a similar vascular pattern to solitary fibrous tumor and, partly for this reason, it and other hemangiopericytomas have been subsumed into solitary fibrous tumor. The present study provides a comprehensive documentation of a single case of pulmonary lipomatous hemangiopericytoma of the lung, the first to be described at this site, and compares it with solitary fibrous tumor, in terms of clinical, histological, immunohistochemical, ultrastructural, and cytogenetic findings. Apart from the lipid-laden-cell component, pulmonary lipomatous hemangiopericytoma and solitary fibrous tumor were similar histologically. Bcl-2 was positive in both. CD34 was minimally expressed in pulmonary lipomatous hemangiopericytoma, which possessed some non-descriptive intercellular junctions, a feature shared by solitary fibrous tumor, which was CD34 positive. However, one of the latter was rich in gap junctions, a feature consistent with strong connexin (Cx) 43 staining and the existence, hitherto unappreciated, of a CD34/Cx43-positive tumor cell network. In pulmonary lipomatous hemangiopericytoma, chromosomal deletions of 43-44, X, -Y were found. In solitary fibrous tumor, 46, XY, del(13)(q?) abnormalities and abnormalities involving chromosome 10 were frequently observed. These similarities and differences are discussed in the context of the currently favored diagnostic fusion of hemangiopericytoma and solitary fibrous tumor.

Familial multiple lipomatosis: report of a new family

Familial multiple lipomatosis (FML) is a rare entity. We report a family with this disease. Karyotypic analysis was performed on tissue isolated from excised lipomas and peripheral blood. No chromosomal abnormalities were found. This is the first report of karyotypic analysis of lipomas removed from a patient with FML. The finding of a normal karyotype is important because approximately 25% of spontaneous lipomas will have abnormal karyotypes; therefore, we felt there was a significant probability that familial lipomas in FML would have abnormal karyotypes.

Altered expression of master regulatory genes of adipogenesis in lipomas from patients bearing tRNA(Lys) point mutations in mitochondrial DNA

The mechanisms underlying the appearance of lipomas in patients bearing mutations in the tRNA(Lys) gene of mitochondrial DNA are unknown. We investigated changes in gene expression patterns in lipomas from three patients bearing A8344G or G8363A tRNA(Lys) gene mutations. Uncoupling protein-1 mRNA was detected in the lipomas, in contrast with undetectable expression in normal adipose tissue. However, expression of other markers of brown fat, such as PGC-1alpha, was unaltered. PPARgamma and retinoblastoma gene expression was down regulated in the lipomas, but C/EBPalpha mRNA was not affected. The expression of Pref-1 was dramatically down regulated. Thus, lipomatosis due to tRNA(Lys) mutations is associated with a pattern of altered expression of master regulators of adipogenesis consistent with enhanced proliferation but maintenance of adipocyte features, and with a distorted pattern of brown versus white adipocyte differentiation.

A (9;11)(q34;q13) translocation in a hibernoma

The diagnosis of hibernoma has historically been made by histopathologic examination and finding of characteristic brown fat cells with granular multivacuolated cytoplasm. The diagnosis of hibernoma may be complicated, however, because seemingly diagnostic cells could be mistakenly identified as lipoblasts, leading to the erroneous diagnosis of well-differentiated liposarcoma. Cytogenetic alterations in lipomatous tumors are well established and could be used for diagnostic purposes. Previous cytogenetic abnormalities reported in hibernomas have included alteration of 11q13 region. Here, we present a case of a hibernoma with a novel cytogenetic alteration involving a reciprocal translocation between 9q and 11q that was useful in establishing the final diagnosis.

A thoracic wall lipoblastoma in a 3-month-old infant: A case report and review of the literature

Lipoblastoma is a rare benign tumor of adipose tissue seen almost always in infancy and early childhood. Lipoblastoma is present in 2 forms which are pathologically identical: circumscribed and diffuse. It is typically located in the extremities, and less frequently in head-neck region, trunk, and various organs. Lipoblastoma is a tumor with good prognosis with no reported metastases, despite its potential for local invasion and rapid growth. Our patient was a 3-month-old boy who was brought to our clinic for rapidly growing mass in the right hemithorax. With the aim of both diagnosis and treatment, the lipomatous mass was removed by local resection. In addition to the patient's age, histologic and cytogenetic analyses assisted the diagnosis of diffuse lipoblastoma. In the postoperative period, the thorax wall was unaffected, and after 6 years of follow-up no recurrence was observed. In the English literature, 8 cases of thoracic wall lipoblastoma have been previously reported, and only 3 of diffuse form. Here, we report, at our knowledge, the fourth case of thoracic diffuse lipoblastoma, in which cytogenetic analysis showed a previously undescribed karyotype aberration involving chromosomes 8, 13, and 16.