Collision tumor comprising metastatic cholangiocarcinoma and seminoma in an undescended testis: a case report.

Testicular metastasis of solid tumors is uncommon. Common primary sites of metastatic tumors to the testis are the lungs and prostate. Cryptorchidism is associated with a four-fold increase in the risk of a testicular germ cell tumor of which seminoma is the most common type. We report an extremely rare case of a collision tumor that comprised testicular metastasis of intrahepatic cholangiocarcinoma and a seminoma in an undescended testis. To the best of our knowledge, this is the first case of this type of tumor to be described. Awareness that metastatic intrahepatic cholangiocarcinoma may present as a testicular tumor may aid diagnosis and management of such patients.