Benign Collision Tumor of the Ovary Comprising Serous Cystadenoma and Thecoma in an Adolescent Female: A Rare Case Report

Abstract

Collision tumors of the ovary are rare pathological entities defined by the coexistence of two histologically distinct neoplasms within the same ovary, with no microscopic admixture of their cellular components. The pairing of a benign serous cystadenoma and an ovarian thecoma is among the rarest such combinations, and its occurrence in an adolescent female is exceptional. We report a 16-year-old girl who presented with right iliac fossa pain and menstrual irregularities of four months' duration. Imaging revealed a large right adnexal mass with mixed solid–cystic morphology that raised concern for malignancy. Histopathological examination of the surgically excised specimen confirmed a benign collision tumor comprising a serous cystadenoma and a thecoma with a remnant cystic follicle, with no evidence of malignancy in either component. This case underscores the indispensable role of histopathology in distinguishing this entity from complex malignant neoplasms, and highlights its critical implications for fertility-preserving management in young patients.