Peritoneal desmoplastic small round cell tumors with divergent differentiation: a review

Desmoplastic Small Round Cell Tumor

Desmoplastic small round cell tumor (DSRCT) is an aggressive small round cell neoplasm which predominantly occurs intra-abdominally in adolescents and young adults with a male predominance, and which is characterized by a recurrent t(11;22)(p13;q12) translocation leading to formation of the EWSR1-WT1 fusion gene, which generates a chimeric protein with transcriptional regulatory activity. Histologically, DSRCT has a characteristic morphology, of islands of monotonous small cells within prominent sparsely cellular fibroblastic stroma, and immunohistochemically it shows polyphenotypic multidirectional differentiation, with expression of epithelial, muscle, and neural markers. However, DSRCT can arise more rarely in other sites and exhibit a spectrum of both histologic features and immunoprofile, which may confuse diagnosis with other small round cell neoplasms. Correct diagnosis is important to ensure correct treatment and prognostication; DSRCT are almost universally fatal neoplasms with patients usually succumbing to disease within the first 2 years of diagnosis. While combination treatment strategies can confer a survival benefit, the overall prognosis remains poor. Further insight into the tumorigenic molecular changes generated by the fusion oncogene may lead to the generation of specific targeted therapies. We review DSRCT, discussing morphology and immunohistochemistry, molecular genetic findings, potential targeted treatments, and the differential diagnosis.

Ewing sarcoma/peripheral primitive neuroectodermal tumor and related tumors

Ewing sarcoma/peripheral primitive neuroectodermal tumor (EWS/pPNET) and other tumors with EWS gene rearrangements encompass a malignant and intermediate neoplasm with a broad anatomic distribution and a wide age range but a predilection for soft tissue in children, adolescents, and young adults. The overlapping histologic, immunohistochemical and cytogenetic and molecular genetic features create diagnostic challenges despite significant clinical and prognostic differences. Ewing sarcoma is the 3rd most common sarcoma in children and adolescents, and desmoplastic small round cell tumor is a rare neoplasm that occurs more often in older children, adolescents, and young adults. Pathologic examination is complemented by immunohistochemistry, cytogenetics, and molecular genetics. This article reviews the clinicopathologic features of EWS/pPNET and desmoplastic small round cell tumor in the spectrum of tumors with EWS gene rearrangements. Other tumors with different histopathologic features and an EWS gene rearrangement are discussed elsewhere in this volume.

Desmoplastic small round cell tumor presenting in the ovaries: report of a case and review of the literature

Desmoplastic small round cell tumor is a recently recognized clinical entity with specific morphologic, immunocytochemical, and genetic features. Though this tumor is mostly described to involve serosal surfaces, we report a case with ovarian involvement. The clinical presentation and differential diagnoses as well as the treatment including aggressive surgical debulking and multiagent chemotherapy are discussed.

Role of electron microscopy and other special techniques in the diagnosis of childhood round cell tumors

A series of case presentations show unique challenges associated with childhood round cell tumors and the role of ancillary techniques in diagnosis. Electron microscopy is shown to be the most powerful individual technique. Immunohistochemistry is less effective but also essential. Other ancillary techniques may provide needed additional diagnostic information. Because this is an area where it is of great importance to secure the most rapid, accurate, and specific diagnosis possible, an integrated multimodal approach is recommended--incorporating light microscopic, electron microscopic, and immunohistochemical studies as a matter of routine, and providing for cytogenetic and/or molecular diagnostic studies as indicated.

Desmoplastic small round cell tumor: RT-PCR analysis and immunohistochemical detection of the Wilm's tumor gene WT1

Desmoplastic small round cell tumor is an aggressive neoplasm first described in 1991. Recently, a reciprocal translocation t(11;22)(p13;q12) has been characterized by conventional cytogenetic studies and molecular analysis. This translocation involves the Ewing's sarcoma gene on chromosome 22 and the Wilms' tumor gene WT1 on chromosome 11. The chimeric transcript corresponding to the fusion gene could be detected by the reverse transcriptase-polymerase chain reaction (RT-PCR). Using an anti-WT1 antibody, the WT1 part of the putative chimeric protein could be recognized by immunohistochemistry. We describe two well-characterized cases of intraabdominal desmoplastic small round cell tumor in two male patients aged 14 and 28 with both RT-PCR analysis and immunostaining for WT1. In this report, we insist on the necessity to increase the RT-PCR analysis in DSRCT in order to obtain a precise differential diagnosis. In addition, WT1 immunostaining may serve as a useful diagnostic marker for DSRCT.

Desmoplastic small round cell tumor: I: a histopathologic study of 39 cases with emphasis on unusual histological patterns

The clinical and histological features of 39 cases of desmoplastic small round cell tumor (DSRCT) diagnosed at M.D. Anderson Cancer Center are presented. Thirty-two of the patients were men and seven were women ranging in age from 10 to 41 years (mean, 25 years). Twenty-five of the 35 patients for whom follow-up information was available died of widespread metastases 8 to 50 months (mean, 25.2 months) from the time of their diagnosis and the remaining 10 were alive with disease. With the exception of two cases that occurred in the liver and in the scrotum, respectively, all of the cases originated within the abdominal and/or pelvic peritoneum. Eight tumors also involved the retroperitoneum. Although the characteristic histologic pattern of "small, blue cells" embedded in a dense fibrous stroma was seen in most cases, about one third of the tumors exhibited a wide range of morphologic features. The recognition of these uncommon morphologic variants of DSRCT is of paramount importance to avoid a misdiagnosis because these tumors could potentially be confused with other neoplastic conditions.

An intra-abdominal small round cell neoplasm with features of primitive neuroectodermal and desmoplastic round cell tumor and a EWS/FLI-1 fusion transcript

We report an intra-abdominal round cell tumor in a young man which exhibited the light and electron microscopic appearance of a peripheral primitive neuroectodermal tumor (PNET), in addition to the clinical and topographic characteristics, desmoplasia and a complex immunophenotypic profile of the intra-abdominal desmoplastic round cell tumor (DSRCT). Reverse transcription polymerase chain reaction revealed a EWS/FLI-1 fusion transcript as in PNET/Ewing's sarcoma, instead of the EWS/WT1 transcript of DSRCT. The tumor was also strongly positive for the mic2 protein. This is a unique case of a hybrid tumor arising in the peritoneal cavity of a young male. The existence of such a hybrid tumor in this location suggests that DSRCT and PNET may be related and possibly share a common histogenesis.

Disseminated intrathoracic desmoplastic small round-cell tumor: a case report

PURPOSE

Recently recognized as a distinct clinicopathologic entity, desmoplastic small round-cell tumors typically affect young men. These aggressive tumors usually arise in the abdomen; other sites of primary disease have been described only rarely. We report the case of an extraabdominal primary tumor with widespread dissemination, including the subcutaneous tissue, a previously unrecognized metastatic site.

PATIENT AND METHODS

We describe the case of a 16-year-old boy with a primary extraabdominal metastatic desmoplastic small round-cell tumor.

RESULTS

Our patient had a primary intrathoracic desmoplastic small round-cell tumor and widespread dissemination involving the subcutaneous tissue, kidney, liver, bone, and lymph nodes. Histopathologic analysis found intense desmoplasia and polyphenotypic expression of neural, muscle, and epithelial markers. Reverse transcriptase-polymerase chain reaction analysis of fresh tumor tissue confirmed the characteristic EWS-WT1 transcript.

CONCLUSIONS

Broader than originally anticipated, the clinical spectrum of desmoplastic small round-cell tumors continues to evolve. Primary intrathoracic tumors with soft-tissue dissemination and polyphenotypic expression should prompt suspicion of this malignancy. Molecular analysis of fresh tumor tissue is an important adjunct to diagnosing this rare neoplasm.

Detection of the EWS/WT1 gene fusion by reverse transcriptase-polymerase chain reaction in the diagnosis of intra-abdominal desmoplastic small round cell tumor

We report two cases of intra-abdominal desmoplastic small round cell tumor with characteristic clinical, histological, immunohistochemical, and ultrastructural features. Fusion of the EWS gene on chromosome 22 and the WT1 gene on chromosome 11, resulting from the chromosomal translocation t(11;22)(p13;q12), was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in both cases. This translocation has been previously reported in this type of tumor using either cytogenetic or molecular biological techniques. Tumor tissue from both cases revealed no chimeric fusion transcripts characteristic of the Ewing sarcoma family of peripheral primitive neuroectodermal tumors or of alveolar rhabdomyosarcoma, two tumors in the differential diagnosis of intra-abdominal desmoplastic small round cell tumor. This report demonstrates the utility of molecular studies as an adjunct in the diagnosis of this rare and aggressive tumor.

Biphasic intra-abdominal desmoplastic small cell tumor in a patient with proximal spinal muscular atrophy

A case is reported of intra-abdominal desmoplastic small cell tumor (IDSCT) with biphasic histologic features in a patient with proximal spinal muscular atrophy. The tumor was composed of small epithelial cell nests with spindle cell sarcomatous areas. Both areas were surrounded by a desmoplastic stroma. Immunohistochemical studies revealed reactivity for low molecular weight cytokeratin, epithelial membrane antigen, vimentin, desmin and Leu-7 in both areas. Electron microscopic examination demonstrated paranuclear aggregates of intermediate filaments, zonula adherens and basement membrane-like material in the epithelial cells, while spindle cells in the tumor had fewer intracytoplasmic organelles. However, intermediate or transitional forms of both types of tumor cells were frequently observed. Although IDSCT are known to express multi-phenotypes immunohistochemically, attention should be paid to the broad spectrum of cell morphology in these tumors.

Biphasic intraabdominal desmoplastic small round cell tumor: fine-needle aspiration cytology findings

The present report describes the case of a 9-yr-old boy with an abdominal desmoplastic small round cell tumor (DSRCT) which on fine-needle aspiration cytology and histology revealed a biphasic pattern, making initial diagnosis difficult. Epithelial-like clusters of cells and loosely-arranged poorly-differentiated cells with scant cytoplasm associated with cells having a larger nucleus and multinucleated larger cells represented the smears' counter-part of epithelial clusters and lobules and sarcomatous-like tissue recognized in the histologic sections. Multinucleated cells were common in the sarcomatous-like areas of the tumor. The biphasic pattern was highlighted by immunohistochemistry. Keratin and epithelial membrane antigen stained predominantly or only the epithelial component, while desmin diffusely decorated the sarcomatous areas and the epithelial cells as a paranuclear cytoplasmic dot. Immunosera 013 mainly stained the sarcomatous component.

Recent developments in soft tissue tumors

This article reviews the clinicopathological features of several recently described soft tissue tumours, namely ossifying fibromyxoid tumour, angiomyofibroblastoma, epithelioid angiosarcoma, retiform haemangioendothelioma, intra-abdominal desmoplastic small cell tumour, spindle cell liposarcoma and low grade fibromyxoid sarcoma. Conceptual changes are also discussed. These include the relationship between Ewing's sarcoma and peripheral primitive neuroectodermal tumour, the proposed use of the term atypical lipoma for a subset of well differentiated liposarcomas, and the occurrence at a wide variety of sites of inflammatory myofibroblastic lesions of uncertain biological potential. In addition, advances in the study of soft tissue lesions at the molecular and cytogenetic levels are outlined, with particular emphasis on the recent identification of tumour-specific karyotypic abnormalities in a wide variety of sarcomas.