A Rare Case of Clear Cell Carcinoma Associated With Papillary Cystadenoma Originating in the Epididymis

Introduction: Primary malignant neoplasms of the epididymis are rare. In this case report, we describe clear cell carcinoma associated with papillary cystadenoma of the epididymis (PCE). Case Presentation: A 77-year-old man presented with a painless, enlarged left scrotum. Magnetic resonance imaging (MRI) revealed two different abnormal signals in the left epididymis. A left high inguinal orchiectomy and histopathological examination revealed a benign component consistent with PCE and a malignant component showing solid growth with cell nuclear enlargement, atypical mitotic figures, and invasion into surrounding tissues. The final diagnosis was malignant transformation to clear cell carcinoma of PCE. Conclusion: Although this epididymis tumor may follow an indolent course, the presence of areas with higher proliferative potential suggests surgical excision be recommended as definitive treatment.