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

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.

Liposarcoma: molecular genetics and therapeutics

Sarcomas are a group of heterogeneous tumours with varying genetic basis. Cytogenetic abnormalities range from distinct genomic rearrangements such as pathognomonic translocation events and common chromosomal amplification or loss, to more complex rearrangements involving multiple chromosomes. The different subtypes of liposarcoma are spread across this spectrum and constitute an interesting tumour type for molecular review. This paper will outline molecular pathogenesis of the three main subtypes of liposarcoma: well-differentiated/dedifferentiated, myxoid/round cell, and pleomorphic liposarcoma. Both the molecular basis and future avenues for therapeutic intervention will be discussed.

[Molecular biology of soft-tissue sarcomas]

Sarcomas represent a heterogeneous group of tumors with a complex and poorly reproducible classification. However, in the last ten years, several specific genetic alterations have been described allowing a molecular classification with: 1) sarcomas with a specific translocation which can be used as a diagnostic marker. These translocations can be demonstrated by RT-PCR or by FISH with commercially available break apart probes ; 2) sarcomas with simple genomic profile showing amplification of a few genes. Well differentiated liposarcomas, dedifferentiated liposarcomas and intimal sarcomas show a simple genomic profile characterised by MDM2 and CDK4 amplifications associated with amplification of other genes in dedifferentiated liposarcomas ; 3) sarcomas with activating mutations: about 90% of GIST show activating mutation of a receptor tyrosine kinase gene, either KIT or PDGFRA. The most frequent mutation involves exon 11 of KIT followed by exon 9 of KIT and exon 18 of PDGFRA. Demonstration of these mutations is useful for the diagnosis of CD117 negative GIST, for predicting response to imatinib and to explain secondary resistance to imatinib ; 4) sarcomas with inactivating mutations: malignant rhabdoid tumors show biallelic inactivation of INI1 gene with a lost of INI1 expression which can be demonstrated by immunohistochemistry ; 5) other sarcomas usually show a complex genomic profile characterised by numerous gains and losses of genes with a frequent loss of RB1 and alterations of P53. Leiomyosarcomas, pleomorphic rhabdomyosarcomas, pleomorphic liposarcomas, myxofibrosarcomas, poorly differentiated sarcomas (so-called MFH and fibrosarcomas) belong to this category and show no specific molecular abnormality.

Value and limitation of immunohistochemical expression of HMGA2 in mesenchymal tumors: about a series of 1052 cases

The high mobility group A (HMGA2) gene encodes a protein that alters chromatin structure and regulates the transcription of many genes; it is implicated in both benign and malignant neoplasias, but its rearrangements are a feature of development of several mesenchymal tumors. Given its implication in these tumors and particularly adipocytic tumors, and the availability of antibodies usable on paraffin-embedded tissues, we evaluated the immunohistochemical expression of this gene in a series of 1052 mesenchymal tumors. The objective was to define the value and limitations of HMGA2 immunohistochemical expression for histotyping, and compare with molecular data reported in the literature. We thus analyzed 880 cases on tissue microarray and 182 cases on whole sections (211 adipocytic tumors, 628 sarcomas, 213 benign mesenchymal tumors, and 10 normal adipose tissues). A nuclear immunostaining was detected in 86% of conventional and intramuscular lipomas, in 86% of well-differentiated liposarcomas and in 67% of dedifferentiated liposarcomas, as opposed to 16% of other benign adipose tumors and to 15% of non-well-differentiated liposarcoma/dedifferentiated liposarcoma sarcomas. Among benign mesenchymal tumors and lesions, it was detected in 90% of nodular fasciitis and in 88% of benign fibrous histiocytomas with respective specificities of 85 and 100%, and in 90% of aggressive angiomyxoma, contrary to other vulvovaginal tumor types, which expressed HMGA2 only rarely. The normal adipose tissue was always negative for HMGA2. Although not specific, immunohistochemical detection of the HMGA2 protein is helpful for the distinction of normal adipose tissue from well-differentiated lesions, particularly on biopsy or on re-excision. It is less sensitive than MDM2/CDK4 for dedifferentiated liposarcomas diagnosis, but it appears more specific to distinguish dedifferentiated liposarcomas from other poorly differentiated sarcomas. Finally, and may be more importantly, HMGA2 is useful for the diagnosis of benign fibrous histiocytoma, nodular fasciitis and vulvovaginal benign mesenchymal tumors.

[Molecular methods in the diagnosis of sarcoma]

The use of modern molecular techniques has gained importance in the diagnosis of sarcomas in recent years. Each of the analytical methods discussed here has its unique advantages and specific requirements. Cytogenetic screening methods which provide genome-wide information depend on the availability of fresh tissue. With the aid of fluorescence in situ hybridization and RT-polymerase chain reaction, specific events such as translocations in Ewing sarcoma, synovial sarcoma or alveolar rhabdomyosarcoma, as well as gene amplifications in well-differentiated and dedifferentiated liposarcoma or radiation-induced angiosarcoma and deletions in rhabdoid tumors or well-differentiated spindle cell liposarcoma can be detected in fresh and formalin fixed tissues. Molecular methods including Sanger sequencing, pyrosequencing and high resolution melting provide information about specific molecular aberrations on gene level. Here we review the most important molecular techniques currently used in sarcoma diagnosis, describe their relevance for differential diagnosis and point out specific examples.

Can MDM2 analytical tests performed on core needle biopsy be relied upon to diagnose well-differentiated liposarcoma?

Well-differentiated liposarcoma/atypical lipomatous tumor can be difficult to differentiate from benign lipomatous tumors, especially on limited biopsy material. Adjunctive tests for MDM2 (murine double minute 2) have proven useful in whole-tissue sections; however, their utility has not been determined within the increasingly popular core needle biopsy. Herein, we compare the ability of MDM2 immunohistochemistry and MDM2 fluorescence in situ hybridization (FISH) to discriminate benign lipomatous tumors from well-differentiated liposarcoma on core needle biopsies. Well-differentiated liposarcoma (n=17) and an assortment of benign lipomatous tumors (n=37), which had concurrent or previous core needle biopsies, and resection specimens were subjected to both MDM2 immunohistochemistry and MDM2 FISH on both whole-tissue sections and corresponding core needle biopsy sections. Percentage tumor cells positive for MDM2 by immunohistochemistry and an MDM2:CEP12 FISH ratio was calculated in each biopsy and resection specimen pair and the results were compared. MDM2 FISH had a higher sensitivity (100%) and specificity (100%) compared with MDM2 immunohistochemistry (65 and 89%) in core needle biopsies, respectively. In addition, MDM2 immunohistochemistry had a false-positive rate of 11%, compared to 0% with FISH. The average MDM2:CEP12 ratio was similar in the biopsy material compared with the whole-tissue sections in both well-differentiated liposarcoma and the benign lipomatous tumor group of neoplasms. Detection of MDM2 amplification by FISH is a more sensitive and specific adjunctive test than MDM2 immunohistochemistry to differentiate well-differentiated liposarcoma from various benign lipomatous tumors, especially on limited tissue samples.

Adrenocortical carcinosarcoma: a case report and review of the literature

Adrenocortical carcinosarcoma is an extremely rare and aggressive variant of adrenocortical carcinoma characterized by the presence of both carcinomatous and sarcomatous components, with the latter often showing heterologous differentiation. Due to the rarity and unusual histology, it may pose a diagnostic challenge. In order to increase awareness and identify potential diagnostic pitfalls, we report the ninth case of non-functioning adrenocortical carcinosarcoma in a 45-year-old man who presented with worsening epigastric pain and a left large retroperitoneal mass in close proximity to the body/tail of pancreas and third portion of the duodenum with displacement of the kidney without parenchymal invasion and multiple liver nodules detected by computed tomographic scan. On en bloc resection, the tumor grossly did not involve the pancreas, kidney or colon. Histologically, the tumor was composed of two distinct components - an epithelioid component with granular cytoplasm that stained for synaptophysin, Melan-A, calretinin, and vimentin compatible with adrenocortical differentiation, and a pleomorphic to spindled component that was positive for desmin and myogenin, compatible with rhabdomyosarcomatous differentiation. A wedge biopsy of a liver nodule showed morphologic features similar to the epithelial component of the primary tumor. The patient died three months after surgery due to locoregional and distant recurrence. Adrenocortical carcinosarcoma is a rare malignancy that adds to the differential diagnostic considerations for a retroperitoneal epithelioid malignancy. Awareness of this as a possibility will help in distinguishing this tumor from other carcinomas, melanomas, and true sarcomas.

Added Value of Molecular Biological Analysis in Diagnosis and Clinical Management of Liposarcoma: A 30-Year Single-Institution Experience

Background

Treatment decisions and prognosis assessment for liposarcoma is based on a classification that depends on morphological and genetic features. Revisions by experienced referral pathologists are often advocated.

Methods

The process of histopathological classification in referring hospitals and subsequently in a referral center in relation to molecular biological information is evaluated. A total of 331 consecutive liposarcoma patients were evaluated for the added value of histological review at time of referral. Subsequently, cases were reclassified with implementation of present-day molecular information. For all patients, complete data on staging, treatment, and follow-up were available.

Results

Upon histological revision, 15/54 (28%) diagnoses were reclassified in the first decade, 14/65 (22%) in the second, and 14/53 (26%) in the last decade. Molecular biological analysis enabled well-differentiated liposarcoma with or without dedifferentiated component to be better recognized as such and distinguished from myxoid liposarcoma and pleomorphic liposarcoma. Inclusion of cytogenetic information resulted in reclassification after revision in 4/18 (22%) cases in the first decade, 10/38 (26%) cases in the second decade, and 19/75 (25%) cases in the last decade.

Conclusions

This study indicates that liposarcomas are heterogeneous tumors. Expert assessment and implementation of molecular biological analysis are valuable for adequate classification as a basis for treatment decisions.

The clinical relevance of molecular genetics in soft tissue sarcomas

Bone and soft tissue sarcomas are an infrequent and heterogeneous group of mesenchymal tumors including more than a hundred different entities attending to histologic patterns. Research into the molecular aspects of sarcomas has increased greatly in the last few years. This enormous amount of knowledge has allowed, for instance, to refine the classification of sarcomas, improve the diagnosis, and increase the number of therapeutical targets available, most of them under preclinical evaluation. However, other important key issues, such as sarcomagenesis and the cell of origin of sarcomas, remain unresolved. From a molecular point of view, these neoplasias are grouped into 2 main types: (a) sarcomas showing relatively simple karyotypes and translocations, which originate gene fusions (eg, EWS-FLI1 in Ewing sarcoma) or point mutations (eg, c-kit in the gastrointestinal tumors) and (b) sarcomas showing unspecific gene alterations, very complex karyotypes, and no translocations. The discovery of the early mechanisms involved in the genesis of sarcomas, the more relevant signaling pathways, and the development of genetically engineered mouse models could also provide a new individualized therapeutic strategy against these tumors. This review describes the clinical application of some of the molecular alterations found in sarcomas, some advances in the field of sarcomagenesis, and the development of animal models.

Giant fibrolipoma of the spermatic cord

Fibrolipoma of the spermatic cord is extremely rare. A case of giant fibrolipoma of the right spermatic cord is reported here. A 68-year-old man noticed a mass in the right inguinal region, and was admitted to Shizuoka City Shimizu Hospital. Tumorectomy and right orchiectomy were performed. Grossly, the tumor was a well-defined, yellowish white, solid, firm tumor measuring 13 x 10 x 9 cm. The tumor had a thin capsule. The tumor was attached to the right spermatic cord, and was remote from the right testis and epididymis. Microscopically, the tumor was composed of mature adipose tissue (40% in area) and collagenous fibrous tissue (60% in area). No lipoblasts were recognized, and on immunohistochemistry the tumor was negative for MDM2 and CDK4. Neither smooth muscle nor vascular proliferation was recognized. The tumor was diagnosed as giant fibrolipoma of the right spermatic cord. To the best of the author's knowledge, only two cases of fibrolipoma in the spermatic cord, scrotum, and testis have been reported in the English-language literature.

Fine needle aspiration biopsy diagnosis of dedifferentiated liposarcoma: Cytomorphology and MDM2 amplification by FISH

Lipomatous mesenchymal tumors constitute the most common type of soft tissue tumors. Well-differentiated liposarcoma (WDLS) can undergo dedifferentiation to a nonlipogenic sarcoma of variable histologic grade. In the recent literature, amplification of the murine double minute 2 (MDM2) oncogene, which has a role in cell cycle control, has been successful in distinguishing WDLS from benign lesions. We present a case of dedifferentiated liposarcoma diagnosed by fine-needle aspiration (FNA), using cytomorphology and ancillary studies (immunocytochemistry and fluorescent in-situ hybridization). An 85-year old female presented to our institution with a firm soft tissue mass of the right buttock. The FNA showed atypical spindle cells, osteoclast-like giant cells and extracellular dense matrix material. The cell block showed cellular groups of highly atypical spindle cells with osteoid and adipose tissue. Fluorescence in situ hybridization (FISH) studies performed on the cell block demonstrated amplification of the MDM2 gene. In addition, the findings were morphologically compatible with the previously resected retroperitoneal dedifferentiated liposarcoma with areas of osteosarcoma. This rare case illustrates the usefulness of FNA and ancillary studies in the diagnosis and subclassification of soft tissue tumors. To the best of our knowledge, this is the first report of MDM2 FISH positivity in a liposarcoma diagnosed by FNA.

The benefits of molecular pathology in the diagnosis of musculoskeletal disease : part I of a two-part review: soft tissue tumors

Bone and soft tissue metabolic and neoplastic diseases are increasingly characterized by their molecular signatures. This has resulted from increased knowledge of the human genome, which has contributed to the unraveling of molecular pathways in health and disease. Exploitation of this information has allowed it to be used for practical diagnostic purposes. The aim of the first part of this two-part review is to provide an up-to-date review of molecular genetic investigations that are available and routinely used by specialist musculoskeletal histopathologists in the diagnosis of neoplastic disease. Herein we focus on the benefits of employing well characterized somatic mutations in soft tissue lesions that are commonly employed in diagnostic pathology today. The second part highlights the known somatic and germline mutations implicated in osteoclast-rich lesions of bone, and the genetic changes that disturb phosphate metabolism and result in a variety of musculoskeletal phenotypes. Finally, a brief practical guide of how to use and provide a molecular pathology service is given.

Adult-type rhabdomyosarcoma: analysis of 57 cases with clinicopathologic description, identification of 3 morphologic patterns and prognosis

Adult-type rhabdomyosarcoma (RMS) has been classically defined as a pleomorphic sarcoma with desmin expression occurring in adult patients. To reevaluate this entity, we analyzed a series of 57 cases using immunohistochemistry for desmin, myogenin, alpha smooth muscle actin, h-caldesmon, pankeratin AE1/AE3, epithelial membrane antigen (EMA), S100 protein, CD34, MDM2, and CDK4. In this series, there were 36 men and 21 women aged from 22 to 87 years (median: 59). Tumors were mainly located in the lower limbs (27 cases), trunk wall (15 cases), and upper limbs (10 cases). Most tumors were deeply located (51/54) with a size from 1 to 30 cm (median: 8 cm). Cases were classified in 3 histologic categories: spindle cell RMS (25 cases), pleomorphic RMS (16 cases), and mixed type (16 cases). Forty-one tumors were grade 3 and 16 grade 2. Immunohistochemistry showed that every case was positive for desmin and myogenin. Alpha smooth muscle actin was positive in 21%, pankeratin AE1/AE3 in 20%, and CD34 in 13.2%. Treatment modalities and follow-up were available in 46 cases. Median follow-up was 60.9 months. Eight patients developed a local recurrence and 16 a distant metastasis with a 5-year overall survival rate of 52.6% and a 5-year metastasis-free survival of 62.9%. The only predictive factor for metastasis was histologic grade. In conclusion, adult-type RMS is a rare sarcoma occurring mainly in the extremities and trunk wall with 2 main histologic patterns, spindle cell, and pleomorphic patterns, which represent the end of the spectrum of a single entity.

Fluorescence in situ hybridization in the diagnosis of soft tissue neoplasms: a review

This paper presents an overview of the role of fluorescence in situ hybridization (FISH) in the diagnosis of soft tissue neoplasms. Many soft tissue neoplasms harbor characteristic translocations or amplification of gene regions, which can be assessed by FISH, and can be used to assist in their diagnosis. We discuss the major morphologic categories in which FISH has come to be used including high-grade round cell sarcomas, spindle cell sarcomas, low-grade myxoid neoplasms, adipocytic neoplasms, and malignant melanocytic neoplasms on the basis of a recent review of soft tissue neoplasms which were analyzed by FISH. We also review the molecular alterations (translocations and amplification of gene regions), which have come to define many of these diagnostic entities and the most effective way to evaluate them with FISH with attention to potential pitfalls. Finally, we discuss the advantages and disadvantages of FISH as a technique when appraising soft tissue neoplasms.

Adjuvant chemotherapy in localized soft tissue sarcomas: still not proven

Soft tissue sarcoma is a rare and heterogeneous group of tumors in terms of histological subtypes, molecular alterations, clinical presentation, and prognosis. Yet, these tumors are most often treated similarly in the localized phase. The standard treatment of these patients requires multidisciplinary management, in particular, careful diagnostic procedures and surgery by an expert physician, preceded or followed by external radiotherapy. The utility of adjuvant chemotherapy has been explored in 14 trials comparing adjuvant chemotherapy with no treatment. Several trials reported a lower risk for local relapse and lower risk for metastatic relapse, but only a few small trials reported longer overall survival. A meta-analysis of all trials failed to demonstrate a significant difference in the relapse-free survival (RFS) or overall survival rates. Two additional trials, reported afterward, presented conflicting results, with a significant benefit in terms of the RFS rate for the trial of the Italian Sarcoma Group, but no difference in the RFS or overall survival rate in the most recent European Organization for Research and Treatment of Cancer trial. We conclude that adjuvant chemotherapy has not been proven to improve the outcome of an unselected population of patients. Several hypotheses are proposed to account for this observation.

Molecular pathology of sarcomas: concepts and clinical implications

The molecular genetic changes that have been described in sarcomas over the past era have aided our understanding of their pathogenesis. The majority of sarcomas carry nonspecific genetic changes within a background of a complex karyotype. These constitute the challenges in sarcoma research for unraveling a putative multistep genetic model, such as for chondrosarcoma, and finding targets for therapeutic strategies. Approximately 15-20% of mesenchymal tumors carry a specific translocation within a relatively simple karyotype. The resulting fusion products act either as transcription factors upregulating genes responsible for tumor growth, as for instance in Ewing sarcoma, or translocate a highly active promoter in front of an oncogene driving tumor formation, as for instance in aneurysmal bone cyst. In addition, a small subset of mesenchymal tumors have specific somatic mutations driving oncogenesis. The specific genetic changes unraveled so far had great impact on the classification of bone and soft tissue tumors. In addition, these changes can assist the pathologist in the differential diagnosis of some of these entities, especially within the groups of small blue round cell tumors and spindle cell tumors, if performed in specialized centers. While a putative association between certain fusion products and outcome is still under debate, the role of predicting response of targeted therapy has been well established for KIT and PDGFRA mutations in gastrointestinal stromal tumors.

Soft tissue tumors: new perspectives on classification and diagnosis

BACKGROUND

In recent years, new tumor entities have been described and previously known tumor types have undergone a reassessment. This article offers an overview of recent developments in the classification and interpretation of soft tissue tumors.

METHODS

Selective review of publications from 1990 until 2008 from the literature database of the Consultation and Referral Center for Soft Tissue Tumors in Jena. The current status of the classification and morphological diagnosis of these tumors is described.

RESULTS

The description of the biological behavior of soft tissue tumors has become more detailed with the introduction of two intermediate categories ("intermediate, locally aggressive" and "intermediate, rarely metastasizing"). There have also been some changes in terminology. Previously established terms such as "malignant fibrous histiocytoma" or "hemangiopericytoma" will be used much less often in future, because these tumor types have been reinterpreted. The WHO recommends that highly differentiated liposarcoma be renamed "atypical lipomatous tumor." Molecular diagnostic techniques have become firmly established as an ancillary diagnostic method. The importance of molecular tumor characterization for individually tailored therapy is already becoming clear.

CONCLUSIONS

Optimal diagnosis is the prerequisite for effective therapy and can be achieved only with state-of-the-art knowledge of the pathology of soft tissue tumors.

Pseudosarcomatous fibroblastic/myofibroblastic proliferation in perinephric adipose tissue adjacent to renal cell carcinoma: a lesion mimicking well-differentiated liposarcoma

Cytologically atypical stromal cells were found in the perinephric adipose tissue, mimicking well-differentiated liposarcoma in 12 of 59 (20%) consecutive nephrectomy specimens that were resected for renal cell carcinoma. Morphologically, the atypical cells included enlarged, hyperchromatic spindle cells and floret-type multinucleate cells. Of 59, 10 (17%) renal cell carcinomas invaded through the renal capsule into the perinephric adipose tissue. Of these cases, three (30%) contained the aforementioned atypical cells. In contrast, 9 of 49 cases without extrarenal invasion (18%) contained the atypical stromal cells. Of the 12 cases with atypical stromal cells, 3 (25%) were associated with extrarenal involvement. The atypical spindle cells exhibited focal to variable positivity for smooth muscle actin and desmin in 3 of the 14 cases (including two cases from our consultation files) each. Cytokeratin AE1/AE3, cytokeratin Cam 5.2, cytokeratin 7, epithelial membrane antigen, and S-100 were negative in all cases. Amplification of MDM2 gene region, which is commonly observed in well-differentiated liposarcoma, was absent by fluorescence in situ hybridization (FISH) in the atypical stromal cells. Immunohistochemistry and FISH suggest that the atypical cells are most consistent with reactive fibroblasts/myofibroblasts. Recognition of these atypical fibroblasts/myofibroblasts may help in avoiding the potential pitfall of misdiagnosing them as well-differentiated liposarcoma.

Well-differentiated and dedifferentiated liposarcomas

Atypical lipomatous tumor or well-differentiated liposarcoma (ALT-WDLPS) and dedifferentiated liposarcoma (DDLPS) share the same basic genetic abnormality characterized by a simple genomic profile with a 12q14-15 amplification involving MDM2 gene. These tumors are the most frequent LPS. This paper reviews the molecular pathology, general clinical and imaging features, histopathology, new diagnostic tools, and prognosis of ALT-WDLPS and DDLPS.

Recurrent dedifferentiated liposarcoma of mediastinum involving lung and pleura

We report a case of primary recurrent mediastinal dedifferentiated liposarcoma with unusual long-term survival. A woman who complained of dyspnea showed on imaging features a bulky posterior mediastinal mass which was completely excised and initially misdiagnosed as an angiomyolipoma. She recurred 15 months later and histological examination showed a dedifferentiated liposarcoma. Resection was incomplete and the patient received adjuvant therapy. Eight years later a second recurrence occurred in the right pleura and lung. The patient died three months later.

Liposarcoma or lipoma: does genetics change classic imaging criteria?

Differentiating benign from malignant fatty tumours has always been very difficult for both radiologists and pathologists. Cytogenetic and molecular genetic analyses provide complementary tools for differentiating soft tissue tumours. Our objective was to compare imaging criteria of malignancy with a new diagnostic gold standard, namely, pathological analysis combined with cytogenetic and molecular genetic analyses. Nineteen patients with a fatty tumour were included. All had computed tomography and/or magnetic resonance imaging examination before any biopsy or surgery. All had histopathological and cytogenetic and/or molecular genetic analyses. The imaging diagnosis of benign or malignant lesions was accurate in 15 cases, with 4 false positives for malignancy. Erroneous criteria were a large size (4 cases), and a mass that was not purely fatty. In conclusion, the main pitfall for a false positive radiological diagnosis of liposarcoma is certainly a large-sized tumour. Cytogenetic and molecular genetic analyses contribute to the diagnosis and can be performed at the same time with a core biopsy.

Recurrent RECQL4 imbalance and increased gene expression levels are associated with structural chromosomal instability in sporadic osteosarcoma

Osteosarcoma (OS) is an aggressive bone tumor with complex abnormal karyotypes and a highly unstable genome, exhibiting both numerical- and structural-chromosomal instability (N- and S-CIN). Chromosomal rearrangements and genomic imbalances affecting 8q24 are frequent in OS. RECQL4 gene maps to this cytoband and encodes a putative helicase involved in the fidelity of DNA replication and repair. This protective genomic function of the protein is relevant because often patients with Rothmund-Thomson syndrome have constitutional mutations of RECQL4 and carry a very high risk of developing OS. To determine the relative level of expression of RECQL4 in OS, 18 sporadic tumors were studied by reverse transcription-polymerase chain reaction. All tumors overexpressed RECQL4 in comparison to control osteoblasts, and fluorescence in situ hybridization analysis of tumor DNA showed that expression levels were strongly copy number-dependent. Relative N- and S-CIN levels were determined by classifying copy number transitions within array comparative genomic hybridization profiles and by enumerating the frequency of break-apart fluorescence in situ hybridization within 8q24 using region-specific and control probes. Although there was no evidence that disruption of 8q24 in OS led to an elevated expression of RECQL4, there was a marked association between increased overall levels of S-CIN, determined by copy number transition frequency and higher levels of RECQL4.

Gene expression profiling for the investigation of soft tissue sarcoma pathogenesis and the identification of diagnostic, prognostic, and predictive biomarkers

Soft tissue sarcomas are malignant neoplasms derived from mesenchymal tissues. Their pathogenesis is poorly understood and there are few effective treatment options for advanced disease. In the past decade, gene expression profiling has been applied to sarcomas to facilitate understanding of sarcoma pathogenesis and to identify diagnostic, prognostic, and predictive markers. In this paper, we review this body of work and discuss how gene expression profiling has led to advancements in the understanding of sarcoma pathobiology, the identification of clinically useful biomarkers, and the refinement of sarcoma classification schemes. Lastly, we conclude with a discussion of strategies to further optimize the translation of gene expression data into a greater understanding of sarcoma pathogenesis and improved clinical outcomes for sarcoma patients.

Primary retroperitoneal myxoid/round cell liposarcoma is a nonexisting disease: an immunohistochemical and molecular biological analysis

Almost all primary retroperitoneal liposarcomas can be classified as well-/dedifferentiated liposarcoma. Rarely, however, primary retroperitoneal liposarcoma is classified as myxoid/round cell liposarcoma, based on the presence of myxoid areas and vascular crow's feet pattern, which has resulted in a debate on the classification of liposarcoma in the retroperitoneum. Genetically, myxoid/round cell liposarcoma and well-/dedifferentiated liposarcoma are different diseases. Myxoid/round cell liposarcoma is characterized by a translocation causing FUS-CHOP or EWSR1-CHOP fusion, whereas well-/dedifferentiated liposarcoma is characterized by an amplification of the 12q13-15 region, including MDM2 and CDK4 genes. As myxoid/round cell liposarcoma is highly radio- and chemosensitive, differentiation between subtypes is important to optimize treatment. We studied whether primary retroperitoneal liposarcomas diagnosed as myxoid/round cell liposarcoma represent molecularly true myxoid/round cell liposarcoma or are histopathological mimics and represent well-/dedifferentiated liposarcoma. Primary retroperitoneal myxoid/round cell liposarcoma (n=16) were compared to primary extremity myxoid/round cell liposarcoma (n=20). Histopathological and immunohistochemical features were studied. Amplification status of the 12q13-15 region was studied using a multiplex ligation-dependent probe amplification analysis, and FUS-CHOP or EWS-CHOP translocations were studied using RT-PCR. In primary retroperitoneal myxoid/round cell liposarcoma, MDM2 and CDK4 staining was both positive in 12 of 15 cases. In primary extremity myxoid/round cell liposarcoma, MDM2 was negative in 18/20 and CDK4 was negative in all cases. Multiplex ligation-dependent probe amplification showed the amplification of 12q13-15 region in 16/16 primary retroperitoneal myxoid/round cell liposarcomas and in 1/20 primary extremity myxoid/round cell liposarcomas. Translocation was present in all (18/18) primary extremity myxoid/round cell liposarcomas, but absent in all primary retroperitoneal myxoid/round cell liposarcomas. On the basis of immunohistochemical and molecular characteristics, apparent primary retroperitoneal myxoid/round cell liposarcoma can be recognized as well-/dedifferentiated liposarcoma with morphological features mimicking myxoid/round cell liposarcoma. In these cases, treatment should probably be specifically designed as for well-/dedifferentiated liposarcoma. Moreover, finding of myxoid/round cell liposarcoma translocations in a retroperitoneal localization is highly suggestive of metastasis and should prompt search for a primary localization outside the retroperitoneum.

[Modern morphological diagnosis and current classification of soft tissue sarcomas]

Malignant soft tissue tumors are somewhat rare, and thus sufficient experience in diagnostics and therapy of these sarcomas is available as a rule only at specialist centers. The gold standard of morphological diagnosis is still represented by evaluation of HE-stained histological sections. However modern methods of examination are also helpful in diagnosis. Because immunohistochemistry is now used routinely, emphasis in this article is laid on molecular methods with special reference to fluorescence in-situ hybridization (FISH) and reverse transcriptase polymerase chain reaction. Principles of the WHO soft tissue tumor classification are explained, and the changed or expanded interpretation of some tumor entities is illustrated using the example of atypical lipomatous tumors, so-called malignant fibrous histiocytomas and hemangiopericytomas, fibrosarcomas, and inflammatory myofibroblastic tumors.

Detection of MDM2 gene amplification or protein expression distinguishes sclerosing mesenteritis and retroperitoneal fibrosis from inflammatory well-differentiated liposarcoma

Inflammatory liposarcoma is a variant of well-differentiated liposarcoma/atypical lipomatous tumor that consists of a mixture of lymphocytes, histiocytes, scattered atypical stromal cells, mature adipocytes, and rarely lipoblasts. When the inflammatory infiltrate predominates, the morphological features overlap with various fibroinflammatory disorders including sclerosing mesenteritis and retroperitoneal fibrosis, making the diagnosis difficult. Well-differentiated liposarcoma/atypical lipomatous tumor and dedifferentiated liposarcoma have characteristic molecular markers in the form of giant marker and ring chromosomes consisting of amplicons of 12q13-15, which includes MDM2. MDM2 immunohistochemistry (IHC) (Zymed; clone IF2) and dual color fluorescence in situ hybridization utilizing MDM2 (12q15) and chromosome 12 centromeric probes were performed on formalin-fixed and paraffin-embedded specimens from inflammatory well-differentiated liposarcoma (17 cases), sclerosing mesenteritis (14 cases), and idiopathic retroperitoneal fibrosis (10 cases). MDM2 expression as detected by IHC is a very sensitive tool in recognizing inflammatory well-differentiated liposarcoma (17 of 17); however, 21% (3 of 14) and 10% (1 of 10) of sclerosing mesenteritis and retroperitoneal fibrosis, respectively, displayed weak MDM2 immunoexpression. The MDM2 fluorescence in situ hybridization assay was very specific for inflammatory well-differentiated liposarcoma as 15 of 17 (88%) cases showed MDM2 amplification, whereas none of the cases of sclerosing mesenteritis or idiopathic retroperitoneal fibrosis showed amplification. Five cases of retroperitoneal fibrosis were noncontributory secondary to autofluorescence, potentially limiting the usefulness of the assay in certain situations such as inappropriate fixation. Increased MDM2 expression and/or MDM2 amplification can be employed to aid discrimination of inflammatory well-differentiated liposarcoma from fibroinflammatory mimics. MDM2 fluorescence in situ hybridization is a very specific method (100%), but less sensitive (88%), whereas MDM2 expression by IHC is very sensitive (100%), but less specific (83%). Therefore, a positive screen of difficult cases with MDM2 IHC would require confirmation by the fluorescence in situ hybridization. However, lack of MDM2 immunoexpression would rule out the possibility of inflammatory well-differentiated liposarcoma.

NFIB rearrangement in superficial, retroperitoneal, and colonic lipomas with aberrations involving chromosome band 9p22

Lipomas are frequently characterized by rearrangements resulting in the fusion of the HMGA2 gene (12q14.3) with a variety of partners. Chromosome band 9p22 rearrangements occur in about 1% of lipomas. We report here the molecular cytogenetic analysis of five cases of lipoma with a 9p22 aberration, including the first cytogenetic analysis of a colonic lipoma. Three out of the five cases showed a rearrangement of NFIB at 9p22.3. The NFIB rearrangement involved a fusion with HMGA2 in two cases. We have identified an in-frame fusion of the first three exons of HMGA2 with exon 6 of MSRB3 (12q14.3) and exons 8 and 9 of NFIB by using 3'RACE-PCR in a case of superficial lipoma. In a case of retroperitoneal lipoma we found a fusion of HMGA2 with NFIB by fluorescence in situ hybridization analysis. The colonic lipoma was characterized by a t(9;16;19)(p22;q21;q13) with a rearrangement of NFIB and no rearrangement of HMGA2. NFIB belongs to the nuclear factor I transcription family. It has been previously shown to be fused with HMGA2 in one case of lipoma and to be a recurrent partner of HMGA2 in pleormorphic adenoma of salivary glands. We here demonstrate that NFIB can also be rearranged independently from HMGA2, indicating a potentially important role in lipoma pathobiology. Our findings suggest that the rearrangement of NFIB might be associated with deep-seated lipomas, such as retroperitoneal or gastro-intestinal lipomas.

Massive Localized Lymphedema With Unusual Presentations: Report of 2 Cases and Review of the Literature

Massive localized lymphedema is a benign soft tissue lesion that usually presents as a large mass in morbidly obese adults. The diagnosis may be challenging as it can mimic other lesions, including well-differentiated liposarcoma. We report 2 cases of massive localized lymphedema with unusual presentation. The first case is a recurrent massive localized lymphedema in the right thigh of a 40-year-old morbidly obese woman. In addition to typical massive localized lymphedema features such as prominent edema and vascular proliferation in the adipose tissue, we observed prominent and abundant multinucleated stromal floret-like giant cells, arborizing network of capillaries, and areas of hyalinized collagen. Our second case is in a rare location (scrotum extending into penile soft tissue) in an overweight 55-year-old male. This lesion exhibits striking smooth muscle hyperplasia. Lack of staining by antibodies against murine double minute 2 protein and cyclin dependent kinase 4 and absence of high mobility group AT- hook 2 transcription factor rearrangement by fluorescence in situ hybridization support our diagnosis of massive localized lymphedema in both cases.