What's new in adipocytic neoplasia?

Adipocytic tumours are among the most common mesenchymal neoplasms, and constitute a clinically, biologically and pathologically diverse group. Their wide histological spectrum and frequent morphological overlap have made classification and diagnosis challenging, with accurate classification being critical because of the considerable differences in prognosis and management between morphologically overlapping neoplasms. Ongoing advances in molecular genetics have aided significantly to our understanding of these neoplasms, with continuing evolution in classification. This review summarises the new developments in benign and malignant adipocytic neoplasms, with discussion of new entities and genetic findings, updates on the clinical and morphological spectrum, and the use of diagnostic immunohistochemistry and molecular markers in the differential diagnosis.

Genome sequencing analysis of a family with a child displaying severe abdominal distention and recurrent hypoglycemia.

BACKGROUND: Germline mutations in PTEN are associated with the PTEN hamartoma tumor syndrome (PHTS), an umbrella term used to describe a spectrum of autosomal-dominant disorders characterized by variable phenotypic manifestations associated with cell or tissue overgrowth. We report a boy who developed severe progressive abdominal distention due to a dramatic adipose mass from the age of 7 months and developed recurrent hypoinsulinemic hypoglycemia that led to seizures at the age of 4 years. METHODS: Trio-based whole-genome sequencing was performed by using blood DNA from the child and his parents. The possible pathogenic variants were verified by Sanger sequencing. Functional characterization of the identified variant was completed by western blot. RESULTS: The child inherited a single-nucleotide deletion NM_000314.6:c.849delA (p.Glu284Argfs) in the tumor suppressor gene PTEN from his father. The paternal family members have a history of cancer. It is conceivable that PTEN loss-of-function induced the adipose tumor growth and hypoglycemia, although the proband did not meet the usual diagnosis criteria of Cowden syndrome or Bannayan-Riley-Ruvalcaba syndrome that are characterized by germline mutations of PTEN. CONCLUSION: This case underlines the variability of phenotypes associated with PTEN germline mutations and provides useful information for diagnosis and genetic counseling of PTEN-related diseases for pediatric patients.

Molecular updates in adipocytic neoplasms✰.

Adipocytic neoplasms include a diversity of both benign tumors (lipomas) and malignancies (liposarcomas), and each tumor type is characterized by its own unique molecular alterations driving tumorigenesis. Work over the past 30 years has established the diagnostic utility of several of these characteristic molecular alterations (e.g. MDM2 amplification in well- and dedifferentiated liposarcoma, FUS/EWSR1-DDIT3 gene fusions in myxoid liposarcoma, RB1 loss in spindle cell/pleomorphic lipoma). More recent studies have focused on additional molecular alterations which may have therapeutic or prognostic impact. This review will summarize several of the important molecular findings in adipocytic tumors that have been described over the past 10 years.

Adipocytic tumors in Children: A contemporary review.

Adipocytic neoplasms in the pediatric population demonstrate a different histologic spectrum and frequency than in adults. The vast majority of these tumors are benign, with lipoma being the most common entity. The identification of signature cytogenetic and molecular alterations for certain lesions, such as PLAG1 gene rearrangement in lipoblastoma and FUS-DDIT3 fusion in myxoid liposarcoma, has been helpful in approaching these neoplasms and aiding in confirming the diagnosis. Furthermore, it is important for pathologists to recognize that adipocytic neoplasms may be associated with different syndromes with potential impact in managing such patients. This review provides a summary of the clinical pictures, histologic characteristics, molecular alterations, differential diagnoses, and syndromic associations of the commonly encountered fatty tumors in children.

Tumours composed of fat are no longer a simple diagnosis: an overview of fatty tumours with a spindle cell component.

This is a review of the morphological spectrum of fatty tumours containing a component of spindle cells, highlighting the immunohistochemical and cytogenetic workup that is now mandatory for accurate diagnosis, with the goal of providing a practical approach for practising surgical pathologists. There have been significant advances in recent years in classifying and understanding the pathogenesis of fatty tumours with spindle cells, based on the correlation of histological, immunohistochemical and cytogenetic/molecular findings. In spite of this, morphological diagnosis and accurate classification of fatty tumours with spindle cells can be challenging to diagnostic pathologists. A group of three lesions: spindle cell lipoma, mammary-type myofibroblastoma and cellular angiofibroma share morphological features and are united by retinoblastoma protein (pRb) loss. Closely allied to these lesions, especially spindle cell lipoma is the newly designated atypical spindle cell lipomatous tumour, which shares morphological, immunohistochemical and cytogenetic features with the trio of tumours lacking nuclear pRb. All of these lesions lack MDM2 and CDK4 amplification as well and separation is based on clinical features, principally location. Atypical lipomatous tumour or well-differentiated liposarcoma shows retention of pRb but overexpression and amplification of MDM2. Fatty tumours with spindle cells need to be extensively sampled, with careful attention paid to cellular atypia and location, and they need to have immunohistochemical workup with pRb, MDM2, desmin, CD34 and p16. In addition, cytogenetic analysis for MDM2 and CDK4 amplification has become crucial for the proper identification of these lesions.

Loss of the tumour suppressor gene AIP mediates the browning of human brown fat tumours.

Human brown fat tumours (hibernomas) show concomitant loss of the tumour suppressor genes MEN1 and AIP. We hypothesized that the brown fat phenotype is attributable to these mutations. Accordingly, in this study, we demonstrate that silencing of AIP in human brown preadipocytic and white fat cell lines results in the induction of the brown fat marker UCP1. In human adipocytic tumours, loss of MEN1 was found both in white (one of 51 lipomas) and in brown fat tumours. In contrast, concurrent loss of AIP was always accompanied by a brown fat morphology. We conclude that this white-to-brown phenotype switch in brown fat tumours is mediated by the loss of AIP. Copyright © 2017 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

FXYD5 (dysadherin) may mediate metastatic progression through regulation of the ß-Na+-K+-ATPase subunit in the 4T1 mouse breast cancer model.

FXYD5 is a Na+-K+-ATPase regulator, expressed in a variety of normal epithelia. In parallel, it has been found to be associated with several types of cancer and effect lethal outcome by promoting metastasis. However, the molecular mechanism underlying FXYD5 mediated invasion has not yet been identified. In this study, using in vivo 4T1 murine breast cancer model, we found that FXYD5-specific shRNA significantly inhibited lung cancer metastasis, without having a substantial effect on primary tumor growth. Our study reveals that FXYD5 participates in multiple stages of metastatic development and exhibits more than one mode of E-cadherin regulation. We provide the first evidence that FXYD5-related morphological changes are mediated through its interaction with Na+-K+-ATPase. Experiments in cultured 4T1 cells have indicated that FXYD5 expression may downregulate the ß1 isoform of the pump. This behavior could have implications on both transcellular interactions and intracellular events. Further studies suggest that differential localization of the adaptor protein Annexin A2 in FXYD5-expressing cells may correlate with matrix metalloproteinase 9 secretion and adhesion changes in 4T1 wild-type cells.

Correlation of Classic and Molecular Cytogenetic Alterations in Soft-Tissue Sarcomas: Analysis of 46 Tumors With Emphasis on Adipocytic Tumors and Synovial Sarcoma.

INTRODUCTION: Sarcomas are heterogeneous, and their treatment and prognosis are driven by the morphologic subtype and the clinical stage. Classic cytogenetics and fluorescence in situ hybridization (FISH) analysis play an important role in their diagnostic work up. MATERIALS AND METHODS: Forty-six cases of soft-tissue sarcoma were reviewed that underwent karyotyping and simultaneous FISH analysis at initial diagnosis. They included 10 dedifferentiated liposarcomas, 10 myxoid liposarcomas, and 14 synovial sarcomas. Six tumors were investigated for EWSR1 rearrangement. Six high-grade miscellaneous sarcomas were also examined. RESULTS: The dedifferentiated liposarcoma had complex karyotypes and MDM2 amplification by FISH, and of these, 5 tumors with myxoid changes also had complex signals for DDIT3. All but 4 myxoid liposarcomas had complex karyotypes, in addition to the characteristic translocation. FISH analysis displayed DD1T3 rearrangement. All synovial sarcomas except 1 recurrence had a t(X;18) translocation by karyotyping and FISH. The EWSR1 rearrangement was present in all extraskeletal myxoid chondrosarcomas, angiomatoid fibrous histiocytoma, atypical Ewing sarcoma, and a clear-cell sarcoma, all of which had characteristic karyotypes. Seven high-grade sarcomas had no specific karyotype or rearrangements for DDIT3, SS18, and EWSR1 by FISH. CONCLUSIONS: There is good correlation between karyotyping and FISH. Complex FISH signals found in dedifferentiated liposarcomas may be related to an increased chromosome 12 copy number and ploidy. Karyotyping is an important baseline standard for the quality assurance of newly developed FISH probes. It also provides a global view of chromosomal changes and the opportunity to investigate the role of other genetic alterations and potential therapeutic targets.

Subcutaneous panniculitis-like T-cell lymphoma: Pediatric case series demonstrating heterogeneous presentation and option for watchful waiting.

Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) and primary cutaneous gamma delta T-cell lymphoma (PCGD-TCL) were initially both classified as subcutaneous panniculitis-like T-cell lymphoma. In 2008, SPTCL with alpha-beta T-cell receptor subtype was separated from primary cutaneous gamma delta T-cell lymphomas (PCGD-TCL). We report four pediatric cases that demonstrate the heterogeneity of each disease and show that PCGD-TCL in children can have an indolent course, whereas SPTCL can behave aggressively. Three patients had spontaneous, durable remissions without treatment, whereas the one patient with disease progression was treated successfully. Watchful waiting may thus be appropriate for initial management of children.

[Adipocytic tumors]. / Tumeurs adipeuses.

Adipocytic tumors are the most common mesenchymal neoplasms, liposarcoma accounting for approximately 20% of soft tissue sarcomas. The differential diagnosis between benign and malignant tumors is often problematic and represents a significant proportion of consultation cases. The goal of this article is to review liposarcoma subtypes, the main benign adipocytic neoplasms: lipoblastoma, hibernoma, spindle/pleomorphic cell lipoma, chondroid lipoma, as well as non adipocytic neoplasms with a lipomatous component such as lipomatous solitary fibrous tumor, emphasizing on practical differential diagnosis issues, and immunohistochemical and molecular tools allowing their resolution.

Real-time polymerase chain reaction analysis of MDM2 and CDK4 expression using total RNA from core-needle biopsies is useful for diagnosing adipocytic tumors.

BACKGROUND: Diagnosing adipocytic tumors can be challenging because it is often difficult to morphologically distinguish between benign, intermediate and malignant adipocytic tumors, and other sarcomas that are histologically similar. Recently, a number of tumor-specific chromosome translocations and associated fusion genes have been identified in adipocytic tumors and atypical lipomatous tumors/well-differentiated liposarcomas (ALT/WDL), which have a supernumerary ring and/or giant chromosome marker with amplified sequences of the MDM2 and CDK4 genes. The purpose of this study was to investigate whether quantitative real-time polymerase chain reaction (PCR) could be used to amplify MDM2 and CDK4 from total RNA samples obtained from core-needle biopsy sections for the diagnosis of ALT/WDL. METHODS: A series of lipoma (n = 124) and ALT/WDL (n = 44) cases were analyzed for cytogenetic analysis and lipoma fusion genes, as well as for MDM2 and CDK4 expression by real-time PCR. Moreover, the expression of MDM2 and CDK4 in whole tissue sections was compared with that in core-needle biopsy sections of the same tumor in order to determine whether real-time PCR could be used to distinguish ALT/WDL from lipoma at the preoperative stage. RESULTS: In whole tissue sections, the medians for MDM2 and CDK4 expression in ALT/WDL were higher than those in the lipomas (P < 0.05). Moreover, karyotype subdivisions with rings and/or giant chromosomes had higher MDM2 and CDK4 expression levels compared to karyotypes with 12q13-15 rearrangements, other abnormal karyotypes, and normal karyotypes (P < 0.05). On the other hand, MDM2 and CDK4 expression levels in core-needle biopsy sections were similar to those in whole-tissue sections (MDM2: P = 0.6, CDK4: P = 0.8, Wilcoxon signed-rank test). CONCLUSION: Quantitative real-time PCR of total RNA can be used to evaluate the MDM2 and CDK4 expression levels in core-needle biopsies and may be useful for distinguishing ALT/WDL from adipocytic tumors. Thus, total RNA from core-needle biopsy sections may have potential as a routine diagnostic tool for other tumors where gene overexpression is a feature of the tumor.

Absence of chromosomal abnormalities in herniated orbital fat.

AIMS: Lipomatous tumours of the orbit are rare, and can sometimes be difficult to characterize. Herniated orbital fat is thought to be a reactive process, but its presentation can mimic a lipomatous tumour such as an atypical lipomatous tumour or spindle cell/pleomorphic lipoma. Genetic studies to determine if it is indeed a reactive process rather than an adipocytic neoplasm have not been performed. METHODS AND RESULTS: Four samples of herniated orbital fat were reviewed clinically, histopathologically and immunohistochemically. Array comparative genomic hybridization (aCGH) was used to search for genome-wide copy number alterations within the tumours. Histological evaluation revealed that all four tumours contained collections of adipocytes surrounded by fibrous septae. Lochkern cells and floret-like multinucleated giant cells were present, consistent with herniated orbital fat. CD34 was positive in all tumours. Staining for MDM2 and CDK4 was negative. ACGH analysis demonstrated no copy number alterations. CONCLUSIONS: Herniated orbital fat may share some histopathological features with lipoma and atypical lipomatous tumour, but the absence of copy number gains or losses is consistent with the impression that herniated orbital fat is a reactive process. Genetic analysis may be another method to help differentiate herniated orbital fat from a lipomatous orbital tumour when the diagnosis is in question.

Cytogenetic analysis in the diagnosis and management of lipoblastomas: results from a single institution.

BACKGROUND: Lipoblastomas are rare, benign, soft tissue tumors that occur primarily in young children. Treatment includes complete excision and surveillance for recurrence. Lipoblastomas can be indistinguishable from other benign lipomatous tumors and liposarcomas. Cytogenetic analysis can provide the definitive diagnosis in questionable cases, because benign and malignant lipomatous tumors exhibit specific nonrandom cytogenetic abnormalities. The purpose of the present study was to discuss the disease management and outcomes in a large contemporary group of patients with lipoblastoma. MATERIALS AND METHODS: A retrospective chart review of patients diagnosed with lipoblastoma presenting from 2000-2011 was conducted. The data from these patients were compared with data from a previously published historical group of patients (1985-1999) from the same children's hospital. RESULTS: We identified 37 patients in the contemporary cohort group and compared them with 25 patients from the historical group. The tumor involvement sites were similar. The current cohort group had a lower recurrence rate, although this might have been underestimated owing to a shorter follow-up period (median 1.4 y, range 2 wk to 11.0 y). Preoperative imaging findings led to an incorrect diagnosis in 62% of the patients. Cytogenetic analysis was used to help determine the final diagnosis in 50% of the cases. In 39% of cases, translocations involved the long arm of chromosome 8, the most common anomaly in lipoblastoma. CONCLUSIONS: Lipoblastomas are rare tumors in young children that can be misclassified as other malignant or benign lipomatous tumors with markedly different outcomes and treatments. We recommend that cytogenetic analysis be routinely used for all pediatric lipomatous tumors to provide an accurate diagnosis and guide appropriate therapy and follow-up.

Presence of C11orf95-MKL2 fusion is a consistent finding in chondroid lipomas: a study of eight cases.

AIMS: Chondroid lipomas are benign adipose tissue tumours. Their rarity and peculiar morphology can lead to misinterpretation, especially in small biopsies. Based on a recurrent translocation t(11;16)(q13;p13), the C11orf95-MKL2 fusion gene has been found in a few cases. Therefore, it seemed appropriate to look for this fusion gene in a larger cohort. METHODS AND RESULTS: We describe eight further cases from four females and four males with an age range of 21-81 years (median 49 years). The tumours were situated in the lower arm (three), lower leg (two), thigh (one), back (one) and head (one); seven lesions were deep-seated and one was located subcutaneously. Sizes ranged from 3 to 12 cm (median 6.3 cm). All patients were treated by simple excision, and follow-up, available for six patients (range 2 months-12 years; median 15 months), demonstrated recurrence in one case. Histologically, the circumscribed and lobulated tumours showed a variable composition of adipocytes, lipoblasts, hibernoma-like cells and chondroblast-like cells embedded in a chondroid matrix. Immunohistochemistry, performed in four cases, revealed positivity for S-100 and pancytokeratin in two of three neoplasms stained for each marker. A C11orf95-MKL2 fusion gene was shown by RT-PCR analysis in seven of the eight cases. CONCLUSIONS: Molecular analysis can be used to support the diagnosis of chondroid lipoma, especially in small samples. This may be helpful in planning treatment when the differential diagnosis includes malignant lesions.

HMGA2 and MDM2 expression in lipomatous tumors with partial, low-level amplification of sequences from the long arm of chromosome 12.

Ordinary lipomas are cytogenetically characterized primarily by simple balanced chromosome aberrations with stable morphologies, most of which affect chromosome segment, 12q13-15, where the HMGA2 gene plays a key pathogenetic role. Atypical lipomatous tumors (ALTs) display supernumerary ring or giant marker chromosomes with amplification of several genes including HMGA2 and MDM2. A study of HMGA2 expression in a variety of adipocytic tumors showed aberrant expression in lipomas with 12q13-15 aberrations and ring chromosomes as well as in ALTs and well-differentiated liposarcomas (WDLSs), and frequent differential expression of HMGA2 exons 1-2 versus that of exons 4-5. A minor subset of adipocytic tumors harbors unbalanced karyotypes with extra copies of 12q sequences in structures that are not giant marker or ring chromosomes. Out of a series of ten such tumors, three lipomas and four ALTs with more than two copies of 12q13-15 and breakpoints in 12q13-15 could be analyzed by quantitative real-time polymerase chain reaction (qRT-PCR) to find out whether HMGA2 and MDM2 expression was more similar to the levels seen in lipomas with cytogenetically balanced aberrations of 12q13-15, or to ALTs with giant ring or marker chromosomes. One of two ALTs with more complex, hyperdiploid karyotypes had expression levels closer to those seen in ALT, whereas the remaining six cases were similar to lipomas with 12q13-15 changes and ring chromosomes. Differential expression was seen in two ALTs and all three lipomas. Two cases showed MDM2 expression levels similar to those found among WDLSs, two cases showed levels similar to those found among lipomas, whereas the remaining three cases displayed intermediate expression levels. The studied cases represent intermediates between lipoma and ALT, insofar as they shared 12q13-15 rearrangements and karyotypic stability with lipomas and gain of 12q sequences with ALTs. Neither of these characteristics can be used to discriminate between lipoma and ALT.

Contributions of cytogenetics and molecular cytogenetics to the diagnosis of adipocytic tumors.

Over the last 20 years, a number of tumor-specific chromosomal translocations and associated fusion genes have been identified for mesenchymal neoplasms including adipocytic tumors. The addition of molecular cytogenetic techniques, especially fluorescence in situ hybridization (FISH), has further enhanced the sensitivity and accuracy of detecting nonrandom chromosomal translocations and/or other rearrangements in adipocytic tumors. Indeed, most resent molecular cytogenetic analysis has demonstrated a translocation t(11;16)(q13;p13) that produces a C11orf95-MKL2 fusion gene in chondroid lipoma. Additionally, it is well recognized that supernumerary ring and/or giant rod chromosomes are characteristic for atypical lipomatous tumor/well-differentiated liposarcoma and dedifferentiated liposarcoma, and amplification of 12q13-15 involving the MDM2, CDK4, and CPM genes is shown by FISH in these tumors. Moreover, myxoid/round cell liposarcoma is characterized by a translocation t(12;16)(q13;p11) that fuses the DDIT3 and FUS genes. This paper provides an overview of the role of conventional cytogenetics and molecular cytogenetics in the diagnosis of adipocytic tumors.

Utilization of fluorescence in situ hybridization in the diagnosis of 230 mesenchymal neoplasms: an institutional experience.

CONTEXT: Mesenchymal neoplasms harbor characteristic translocations and amplification of gene regions amenable to evaluation by fluorescence in situ hybridization (FISH). OBJECTIVE: To determine the utility of FISH in the diagnosis of mesenchymal neoplasms. DESIGN: Two hundred thirty soft tissue cases analyzed by FISH were reviewed retrospectively. RESULTS: Morphologic patterns where FISH was used included high-grade round cell sarcomas (n  =  67), nonmyogenic spindle cell sarcomas (n  =  40), low-grade myxoid neoplasms (n  =  34), adipocytic neoplasms (n  =  20), and melanocytic neoplasms (n  =  19). Fifty cases did not fit into the previously mentioned categories. SYT FISH (96% of monophasic synovial sarcomas were positive; 0% of malignant peripheral nerve sheath tumor were positive) and DDIT3 FISH (100% of myxoid/round cell liposarcomas; no other neoplasm positive) were very sensitive and specific. EWSR1 FISH was very sensitive and specific in the differential diagnosis of melanocytic neoplasms (88% of clear cell sarcomas were positive; all melanomas were negative). EWSR1 FISH was sensitive among high-grade round cell sarcomas (positive in 100% of desmoplastic small round cell tumors and 96% of Ewing sarcoma/primitive neuroectodermal tumors) but not specific because clear cell sarcoma, extraskeletal myxoid chondrosarcoma, and a subset of round cell liposarcomas also harbor rearrangements of EWSR1. FUS FISH was very sensitive in detecting low-grade fibromyxoid sarcomas (91% positive) but not specific because most myxoid/round cell liposarcomas also contain rearrangements of FUS. All atypical lipomatous tumors were positive for amplification of MDM2, whereas all lipomas were negative. FOXO1A FISH was positive in ∼70% of cases of alveolar rhabdomyosarcoma. CONCLUSION: FISH is a useful adjunct in the diagnosis of mesenchymal neoplasms.

[Atypical lipomatous tumors of the stomach. Clinical, morphological and molecular findings]. / Atypische lipomatöse Tumoren des Magens. Klinische, morphologische und molekularbiologische Befunde.

Two cases of primary gastric atypical lipomatous tumors (ALT) are presented. In case No.1, a 7x4x3 cm submucosal ALT (lipoma-like subtype) of the antrum/pyloric region in a 60-year-old woman was completely resected. Using interphase dual-color-FISH, MDM2- and CDK4 amplifications could be detected in distinguished amplicons. The patient was continuously free of disease after 56 months. In case No. 2, a 3.5 cm (in diameter) submucosal ALT (lipoma-like subtype) of the gastric body in a 56-year-old woman was completely resected. FISH revealed MDM2 amplification while the CDK4 gene remained in diploid copies. This patient was continuously free of disease after 36 months. The morphologic and molecular biological findings of this rare primary gastric mesenchymal tumor are discussed in comparison with the corresponding soft tissue lesions.

PIM-1 kinase expression in adipocytic neoplasms: diagnostic and biological implications.

The differential diagnosis of soft tissue tumours poses a considerable challenge for pathologists, especially adipocytic tumours, as these may show considerable overlap in clinical presentation and morphological features with many other mesenchymal neoplasms. Hence, a specific and reliable marker that identifies adipocytic differentiation is much sought. We investigated the immunohistochemical expression of PIM-1 kinase in 35 samples of soft tissue tumours using tissue microarray technology and 49 full sections of adipocytic (n = 26) and non-adipocytic tumours (n = 23). Benign and malignant adipocytic tumours showed strong expression of PIM-1 while the non-adipocytic tumours were either negative or showed only weak staining for the protein. In myxoid liposarcomas, PIM-1 showed a distinct, unique vacuolar staining pattern, clearly outlining fine cytoplasmic lipid vacuoles. By contrast, non-adipocytic myxoid tumours (myxoma, chordoma and myxoid chondrosarcoma) did not show this vacuolar pattern of PIM-1 staining, although vacuolated cells were present on H&E. This differential expression was confirmed at a gene expression level in selected cases. Our results indicate that the expression of PIM-1 in adipose tissue may be a useful marker of adipocytic differentiation, in particular if the staining is both of high intensity and present in a unique, vacuolar pattern.