Rapidly growing adenomatoid tumor extending into testicular parenchyma mimics testicular carcinoma

A 40-year-old man presented with a 1-month history of a large, painless, rapidly growing right scrotal mass. Examination, ultrasonography, and intraoperative inspection did not exclude an intratesticular tumor, and a radical orchiectomy was performed. Histology was typical for adenomatoid tumor, but gross and microscopic inspection revealed bundles of tumor extending from the tunica albuginea into the testicular parenchyma. In this case the rapid growth, large size, and the inability to exclude an intratesticular origin directed suspicion toward a malignant neoplasm. In hindsight, the tumor's unique pattern of extension into the adjacent testicular parenchyma confounded the preoperative diagnosis.