“A Wolf in Sheep's Clothing”—STK11 Adnexal Tumor, a Recently Described Rare, Aggressive Entity Misdiagnosed as Female Adnexal Tumor of Probable Wolffian Origin (FATWO)

STK11 adnexal tumor is a rare, recently described tumor of female adnexal origin, characterized by pathognomic alterations in the STK11 gene, frequent association with Peutz-Jeghers syndrome, aggressive clinical course and poor prognosis. This tumor presents a diagnostic challenge to pathologists, due to its striking morphologic and immunohistochemical heterogeneity. Owing to its frequent paratubal location, morphologic similarities and nonspecific immunoprofile, STK11 adnexal tumor may be diagnosed as female adnexal tumor of probable Wolffian origin (FATWO). Distinction from FATWO is, however, crucial given the aggressive nature of this tumor in comparison to the usually benign clinical course in FATWOs. We present herein an account of a 35-year-old female patient with a broad ligament mass, initially diagnosed elsewhere as FATWO. The patient developed widespread peritoneal metastasis within 10 months of initial diagnosis, and underwent cytoreductive surgery. Review of the outside pathology slides and microscopic examination of the cytoreductive surgery specimen at our center, with subsequent molecular testing clinched the correct diagnosis of STK11 adnexal tumor.