Objective: The aim of this study is to address difficulties in diagnosis of the extraintestinal gastrointestinal stromal tumor (GIST) when even in ovary is the tumor. One should ever think of the GIST in the case of peritoneal dissemination of the spindle/epithelioid cell tumor. In contrary, the late intraabdominal recurrence of primary both epithelial and non-epithelial tumor of genital tract can be undistinguishable by pure morphology. Complete clinical records and accurate operation field topography are both of great value. Documenting this phenomenon, presented is both late intraabdominal dissemination of primary uterine endometrial stromal sarcoma and massive ovarian involvement by extraintestinal GIST. Design: Two case reports. Setting: Biopsy Lab s.r.o. and Šikl’s Department of Pathology, Charles University and Faculty Hospital, Pilsen. Methods: The two casuistic reports are covered in detail including broad immunohistochemistry (LSAB+, Dako) and genetics (ABI Prism 310, PE/Applied Biosystems). Results: In 75-year-old woman, 5 cm tumor in maximum diameter of the mesentery was diagnosed as an extraintestinal GIST. Multiple peritoneal recurrence occurred ten years later and the tumor has been reclassified as a disseminated endometroid stromal sarcoma. Ultimately, comprehensive search of clinical files confirmed hysterectomy and adnexotomy in 1973. The second case describes 49-year-old woman operated for tumorous obliteration of the small pelvis where a tumor 9 cm in maximum diameter was found. Initially, predominant epitheloid morphology of the tumor led to the diagnosis of primary epithelial malignancy, sex-cord stromal tumor or metastatic melanoma of the ovary. Finally, the help of immunohistochemistry and molecular biology rendered the tumor as an extraintestinal GIST, ovarian primary not excluded.

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