Aggressive uterine sarcoma with rhabdoid features: Diagnosis by peritonealfluid cytology and absence of INI1 gene mutation

We report a primary uterine sarcoma with classic histologic, immunohistoche mical, and ultrastructural features of a malignant extrarenal rhabdoid tumo r (MERT). It arose in a 71-year-old woman who presented with postmenopausal bleeding, ascites, and a right pelvic mass. Malignant cells with rhabdoid morphology were identified by cytologic examination of the peritoneal fluid . Exploratory laparotomy revealed a 10-cm right adnexal mass and disseminat ed peritoneal tumor. Pathologic study showed diffuse expansion of the endom etrial stroma by rhabdoid-like cells with transmural infiltration of the my ometrium and extensive involvement of uterine serosa and right ovary by tum or. Neoplastic cells were immunoreactive for vimentin, cytokeratin, and epi thelial membrane antigen, and cytoplasmic whorls of intermediate filaments were observed by electron microscopy. Fluorescence in situ hybridization (F ISH) studies with chromosome 22-specific probes showed no loss of the INI1 gene, and no coding sequence mutation was identified. HUM PATHOL 32: 884-88 6. (C) 2001 by W.B. Saunders Company.