Tumours of the testis.

Tumours of the testis are common in dogs, uncommon in other domestic animals. Leydig cell tumours, Sertoli cell tumours, and seminomas occur with similar frequencies and not uncommonly in the same testis. Dogs with Sertoli cell tumours may develop female characteristics and become sexually attractive to other males. It is unusual for testicular tumours in dogs to metastasize. Various histological types within the three main categories are described.