Postmenopausal intra-abdominal desmoplastic small cell tumor

Desmoplastic small round cell tumor masquerading as advanced ovarian cancer

Desmoplastic small round cell tumor (DSRCT) is a rare abdominal malignancy usually diagnosed in young adult males. Most patients have widespread disease at presentation, with an organ of origin difficult to ascertain. A 33-year-old female presented to her gynecologist with complaints of suprapubic pressure, abdominal pain, and increased abdominal girth. She had a large intraabdominal tumor on ultrasound, thought to be ovarian cancer. She underwent surgical exploration, which confirmed a malignancy, but the exact etiology was uncertain. Final pathology was consistent with DSRCT. DSRCT is a rare malignancy that can mimic other more commonly seen tumors such as lymphoma and ovarian cancer. When encountering an extensive intraabdominal malignancy of uncertain etiology, DSRCT should be in the differential diagnosis.

Immunohistochemical expression of WT1 by desmoplastic small round cell tumor: a comparative study with other small round cell tumors

Desmoplastic small round cell tumors (DSRCTs) present a reciprocal chromosomal translocation, t(11;22)(p13;q12), that results in fusion of Ewing's sarcoma and Wilms' tumor (WT1) genes. The authors evaluated 15 DSRCTs and 71 other tumors often considered in the differential diagnosis for immunoreactivity using a polyclonal antibody directed against the WT1 part of the chimeric protein resulting from this translocation. WT1 immunostaining was performed on paraffin material using the WT(C-19) antibody after heat-antigen retrieval. All the DSRCTs (15 of 15, 100%) demonstrated strong WT1 nuclear immunoreactivity. Ten of 14 nephroblastomas (71%) disclosed WT1-positive nuclei in accordance with the staining reported by others, and rare and focal nuclear positivity was detected in two of 17 rhabdomyosarcomas. WT1 immunoreactivity was not observed in Ewing's sarcoma/primitive neuroectodermal tumors (zero of 21, 0%), neuroblastomas (zero of 17, 0%), or rhabdoid tumors of the kidney (zero of two, 0%). In nephroblastoma, differential diagnosis with DSRCT was not difficult: Clinical and morphologic data are not similar for these two entities. The current study validates WT1 immunoreactivity as a useful marker to separate DSRCT from other small round cell tumors.