Epididymal cysts in European bison.

We describe gross and histopathology of cysts found in the epididymis of the European bison (Bison bonasus). The material was collected from 107, 3 mo to 20 yr old, free-ranging, culled males from the Białowieza Primeval Forest (Poland). Epididymal cysts were observed in 65 (61%) of bison of varying ages. They were primarily in the head of epididymis and less often in the corpus or tail. The cysts contained opalescent fluid devoid of spermatozoa. They were lined by epithelium resembling that of efferent ducts and appeared to be congenital abnormalities.