Pagetoid spread into the rete testis by testicular tumours.

Germ cell neoplasia of the testis can spread into the rete testis in a pagetoid manner, but this is less often recognized than vascular invasion or direct spread into the tunica albuginea. The rete testis was studied in 71 orchidectomy specimens: 47 with an untreated germ cell tumour, 18 with germ cell neoplasia after treatment with chemotherapy, and six with other tumours. Pagetoid spread into the rete testis was seen in 14 of the 47 cases of germ cell tumour. The cytology of the infiltrating cells was that of intratubular germ cell neoplasia. Hyperplasia of the rete testis was seen in six cases. In three of the four testes with untreated germ cell neoplasia and hyperplasia of the rete, neoplastic cells were seen in the hyperplastic rete epithelium. The two testes with extensive pagetoid involvement of the rete testis by intratubular germ cell neoplasia both had associated hyperplasia of the rete testis. Two of the 18 testes with germ cell neoplasia after chemotherapy had focal hyperplasia. Pagetoid involvement of the rete testis by intratubular germ cell neoplasia is common and may be a cause of hyperplasia of the rete testis.