Adenomatoid tumors represent 30% of all extratesticular masses; only lipoma is more common.

An adenomatoid tumor is a benign neoplasm that originates in the epididymis, most commonly in the tail. Adenomatoid tumors can occasionally occur in the spermatic cord or testicular tunica and can extend into the testis, mimicking a germ cell tumor. Ultrasound typically shows a well-defined hypoechoic extratesticular mass. MR imaging may be helpful in distinguishing this extratesticular neoplasm from an intratesticular mass in the periphery of the testis. Reported MR findings are an extratesticular mass that is slightly hypointense relative to testicular parenchyma on T2-weighted images and usually does not enhance more intensely than the testis on contrast-enhanced images