Intratubular spermatic seminoma in a Fischer-344 rat.

A case of a spontaneous intratubular spermatic seminoma is described in a 98-wk-old Fischer-344 (F-344) rat. The differential diagnosis of spermatic seminoma from the other morphological forms of the tumor was based on the recognition of 3 cell types. The tumor cells were positive for S-100 antigen and cytokeratin. To the best of our knowledge, this is the second case of a seminoma reported in an F-344 rat and the first dealing with electron microscopic and immunohistochemical features of this tumor.