Ultrasound Features of Female Adnexal Tumor of Probable Wolffian Origin (FATWO): A Case Series and Literature Review.

INTRODUCTION: Female adnexal tumor of probable Wolffian origin (FATWO) is an extremely rare gynecologic neoplasm derived from mesonephric duct remnants. It exhibits nonspecific clinical and imaging features, frequently leading to preoperative misdiagnosis. To date, ultrasound findings of FATWO remain poorly characterized, with limited systematic reports. This study summarizes the ultrasonic manifestations of four pathologically confirmed FATWO cases and reviews the literature, aiming to improve preoperative recognition and fill the gap in systematic ultrasound descriptions of FATWO. CASE PRESENTATION: Four patients with pathologically proven FATWO were retrospectively analyzed. All tumors were located in the adnexal region and outside the ovary. Two cases presented as solid hypoechoic masses with clear boundaries and internal blood flow; one showed a cystic-solid mass with septations and mild vascularity; one appeared as a small cystic hypoechoic lesion. Preoperative ultrasound misdiagnoses included fibroma, corpus luteum cyst/endometrioma, granulosa cell tumor, and uterine leiomyoma. Pathologically, all tumors demonstrated typical tubular, cystic, and reticular structures. Immunohistochemistry was positive for CK, inhibin, WT-1, and calretinin, and negative for GATA-3 and PAX8. All patients remained disease-free during follow-up of 16-83 months. CONCLUSION: FATWO typically manifests as a well-circumscribed, extra-ovarian solid or cystic-solid adnexal mass with mild-to-moderate internal blood flow. When these ultrasound features are identified, FATWO should be included in the differential diagnosis to reduce preoperative misdiagnosis.