[Tumor of the mesosalpinx with unclear differentiation].

Female adnexal tumors of probable Wolffian origin (FATWO) are rare tumors, which are mostly localized in the broad ligament or the mesosalpinx. They show high intratumor and intertumor variability of histological patterns (e.g. solid, tubular, cribriform and cystic) with usually unremarkable cellular and nuclear morphology and a lower mitotic rate. In general, they behave in a benign fashion but there are rare cases with malignant transformation, so that careful examination and surveillance are necessary. Differential diagnoses include Sertoli-Leydig cell tumors, metastasized endometrioid carcinoma and the FATWO-like variant of the endometrioid carcinoma of the fallopian tubes. The FATWOs express pancytokeratin, CD10, vimentin, calretinin and inhibin A. Estrogen and progesterone receptors are expressed in a minority of cases, whereas epithelial membrane antigen (EMA) is not detectable.