[Pagetoid spread of intratubular germ cell neoplasia into rete testis forming tumor-like mass].

Intratubular germ cell neoplasia (ITGCN) is the preinvasive phase of testicular germ cell tumors. ITGCN can spread into the rete testis in a pagetoid manner, but there are very few published data about this phenomenon. Furthermore, the tumor-like mass formed by ITGCN with pagetoid spread into the rete testis has not been documented to date, and the present case is the first to be reported. A tumor-like mass was found close to the superior pole of the left testis in a 39-year-old male and was unrelated to the epididymis. Three other nodules of seminoma surrounded by fibroconnective tissue existed next to the mass. Histological sections revealed ITGCN which was characterized by the presence of large and polygonal germ cells exhibiting clear cytoplasm with distinct cell borders. The cytoplasm was rich in glycogen and the cell membrane was immunohistochemically positive for placental alkaline phosphatase. The nuclei had less coarse chromatin than that of seminoma. ITGCN cells spread in between the lining epithelium of the rete and the basement membrane. This characteristic spread was consistent with pagetoid spread into the rete testis.