Intra-abdominal desmoplastic small round-cell tumour with expression of muscle specific actin

Desmoplastic small round cell tumour of the pleura: a case report with further cytogenetic and ultrastructural evidence of 'mesothelioblastemic' origin

A typical case of desmoplastic small round cell tumour of the pleura in a 25-year-old man is described. In addition to the typical histological and immunohistological findings, the EWS-WT1 fusion product was also observed. Ultrastructurally, some tumour cells displayed intracytoplasmic neolumina, with short microvilli characteristic of submesothelial cells. These findings support the theory of a splanchnopleuric intraembryonic mesodermal, 'mesothelioblastemic' origin, both morphologically and cytogenetically.

Desmoplastic small round cell tumor: II: an ultrastructural and immunohistochemical study with emphasis on new immunohistochemical markers

In order to investigate the histogenesis and facilitate the diagnosis of desmoplastic small round cell tumor (DSRCT), 39 cases were studied by immunohistochemical methods using a large battery of antibodies directed against a wide variety of epithelial, mesenchymal, and neural-associated proteins. Sixteen of these tumors were also studied by electron microscopy. Thirty-seven of 39 cases reacted for cytokeratin using a "cocktail" of 3 monoclonal antibodies (CAM 5.2/AE1/AE3), 39/39 for desmin, 24/25 for epithelial membrane antigen, 22/27 for vimentin, 18/25 for neuron-specific enolase, 10/15 for CD57 (Leu-7), 3/19 for synaptophysin, 1/22 for chromogranin, 3/19 for muscle-specific actin, 3/16 for alpha-smooth-muscle actin, 11/16 for CD15 (Leu-M1), 5/12 for CA-125, 6/17 for CD99, 9/10 for MOC-31, 2/6 for NB84, 5/7 for Ber-EP4, and 8/9 for the Wilms tumor (WT1) protein. No staining was obtained in any of the cases tested for cytokeratin 5/6 or 20, neurofilament proteins, glial fibrillary acidic protein, peripherin, CA19-9, thrombomodulin, alphafetoprotein, carcinoembryonic antigen, TAG-72 (B72.3), placental alkaline phosphatase, S-100 protein, HMB-45, myoglobin, or for the two myogenic regulatory proteins myogenin and MyoD1. A frequent ultrastructural finding was the presence of juxtanuclear aggregates of intermediate filaments, but microfilaments with densities or Z-band-like material suggestive of either smooth or skeletal muscle differentiation were not seen in any case. Dendritic-like processes containing microtubules and dense core granules were seen in four tumors and all of these tumors reacted for at least one of the neural markers investigated. Although ultrastructural and immunohistochemical studies confirmed previous observations that DSRCTs present epithelial, mesenchymal, and neural phenotypes, a great variation was found in the frequency of expression of the different markers used to demonstrate each line of cell differentiation. The absence of expression of cytokeratin 5/6 and thrombomodulin together with positive staining for CD15, MOC-31, and Ber-EP4 argues against the possible mesothelial origin that has been suggested for this tumor. Additionally since none of the tumors reacted for myogenin or MyoD1, desmin expression in DSRCT cannot be regarded as evidence of skeletal muscle differentiation. Although the histogenesis of DSRCT remains unknown, it is believed that this tumor originates from a progenitor cell with potential for multiphenotypic differentiation.

Intraabdominal desmoplastic small round cell tumor with EWS/ERG fusion transcript

This report describes an intraabdominal small cell tumor in a 37-year-old woman, with clinical, topographic, and morphologic features highly suggestive of the desmoplastic small round cell tumor. Immunohistochemical analysis revealed a polyphenotypic profile consistent with this tumor--positivity for keratin, epithelial membrane antigen, neuron-specific enolase, vimentin, and desmin--but, in addition, a strong membranous immunoreactivity for CD99 (MIC2 protein). Reverse transcription polymerase chain reaction revealed a EWS/ERG fusion transcript characteristic of the Ewing's sarcoma/peripheral primitive neuroectodermal tumor group of tumors, rather than the EWS/WT1 chimeric transcript typical of the desmoplastic small round cell tumor. This is the third report of a hybrid tumor with features of the desmoplastic small round cell tumor and Ewing's sarcoma/peripheral primitive neuroectodermal tumor, and the first one with the EWS/ERG fusion gene. Our case shows the existence of some overlap between these two groups of tumors, which are considered to be histogenetically different, and the need for further studies of molecular characterization of small cell tumors, especially in those with atypical morphologic or immunohistochemical features.

Desmoplastic small round cell tumour of childhood: a report of four cases demonstrating wider clinical features and variable outcome

Purpose. Four further cases of desmoplastic small round cell tumour with multi phenotypic differentiation are described.Subjects. Two patients were typical (male, adolescent with peritoneal tumour and, in one case, liver metastases) and did not respond well to treatment. Two other patients showed less usual features (young, female with retroperitoneal disease, both with intraspinal extension and renal tract obstruction). Both responded favourably to multi-modal treatment regimens including extensive and invasive supportive care.Results. Histologically, all tumours showed clear features of this diagnosis, namely angulated nests of small cells in a background of fibrovascular stroma. Immunohistochemistry typically showed divergent differentiation with neural, muscle and epithelial marker positivity. All four tumours stained positive for the Wilms' tumour 1 suppressor gene product. Electron microscopy showed intercellular tight junctions, cytoplasmatic intermediate filaments and absence of microvilli. Rare neurosecretory-type granules were observed.Discussion. These cases illustrate a broader spectrum of clinical presentation than previously associated with this diagnosis.

Postmenopausal intra-abdominal desmoplastic small cell tumor

Intra-abdominal desmoplastic small cell tumor (DSCT) usually occurs in infants and young male adults. A case of DSCT occurring in a 60 year old female is described. No other apparent primary origin was detected. A mesocolon tumor, measuring 23 x 12 x 10 cm, was composed predominantly of round to spindle cells which showed epithelioid- and focally sarcomatous arrangements. Immunohistochemically, the tumor cells showed perinuclear dot-like staining of CAM5.2, many cells expressed HHF35, and some cells contained vimentin, epithelial membrane antigen, desmin, alpha-smooth muscle actin, neuron-specific enolase, or Leu 7. Electron microscopic examination showed that the tumor cells had mesenchymal-fibroblastic features. The tumor had an aneuploid DNA content with high S-phase fraction. The patient, who was treated with adjuvant chemotherapy, was alive, having had three recurrences in 36 months. In the second and third recurrent lesions, increased cellular atypia and fascicular arrangements of spindle cells were observed. DSCT should be included in differential diagnoses of post-menopausal pelvic tumors which show light-microscopically and immunohistochemically divergent phenotypes.