Female adnexal tumor of probable wolffian origin: morphological, immunohistochemical, and ultrastructural study with c-kit gene analysis.

Female adnexal tumors of probable wolffian origin (FATWO) are rare neoplasms believed to originate from mesonephric (wolffian) remnants. Rarity and variable location of FATWO make the diagnosis difficult. Although most cases follow a benign clinical course, approximately 10% of them either recur or metastasize and are thought to be resistant to chemoradiation therapy. In 2004, imatinib therapy, a tyrosine kinase inhibitor known to be effective against gastrointestinal stromal tumors, was reported to be effective also in a case of KIT-positive FATWO. However, c-kit gene mutations in FATWO have never been studied. Herein is reported the case of a 50-year-old Japanese woman with FATWO arising in the right paratubal site. The tumor had typical characteristics of FATWO in both morphology and immunohistochemistry. KIT protein was diffusely and weakly expressed, but DNA analysis revealed no mutational change in exon 9 or 11 of the c-kit gene. It is believed that accumulation of such genetic data of FATWO are essential from a therapeutic standpoint, although the present case had no mutation. In addition, the cytological features of this rare tumor are presented, which have not been described previously.