Granular cell tumor of the testicular tunica albuginea: a case report.

Granular cell tumor (GCT) is exceedingly rare in the genitourinary tract. We report a case of GCT arising in the tunica albuginea of the testis. A 42-year-old male presented with a painless left testicular mass. Scrotal ultrasound studies showed an intratesticular mass that was suspicious for a testicular malignancy; a left orchiectomy was subsequently performed. Grossly, there was a well-circumscribed tumor mass in the periphery of the testis abutting the tunica albuginea. Microscopically, the tumor was poorly delimited and located in the tunica albuginea with minimal infiltration to the underlying testicular parenchyma. The lesion consisted of clusters and sheets of large polygonal cells dissected by fibrous septa. The tumor cells had indistinct cellular borders, abundant granular eosinophilic cytoplasm, and small nuclei with indistinct nucleoli. No cytologic atypia or increased mitotic activity was seen. Immunohistochemically, the tumor cells were positive for S-100, inhibin-α, and CD68 and negative for calretinin, Melan-A, and WT-1. Ki-67 showed a low proliferation index (<1%). The morphology, in conjunction with immunohistochemical profile, led to a diagnosis of GCT of the tunica albuginea. Although GCT can occur in almost any location of the body, it has not been described to involve the human testis.