Reclassification of a tubal leiomyosarcoma as an eGIST by molecular evaluation of c-KIT

Background.Extragastrointestinal stromal tumors (eGISTs) are rare mesenchymal-derived tumors arising outside of the GI tract. eGISTs are often histologically confused with leiomyosarcoma. Distinction between eGIST and leiomyosarcoma is critical because of the unique responsiveness of eGISTs to the molecularly targeted agent imatinib.Case.A woman presented with a history of tubal spindle cell tumor that was initially diagnosed and treated as a leiomyosarcoma. Because of minimal response to sarcoma directed chemotherapy, the possibility that the tumor was in fact an eGIST was investigated and supported by immunohistochemical and mutational analyses of the c-Kit receptor tyrosine kinase. The patient currently has stable disease control on imatinib for the last 18 months.Conclusions.The possibility of eGIST should be considered in the differential diagnosis of tumors with a spindle cell morphology in the gynecologic tract especially when involving the ovary, fallopian tube, or uterine serosa.