Viral-like particles associated with naturally occurring transmissible venereal tumor in two dogs: preliminary report.

Naturally occurring canine transmissible venereal tumors in 2 dogs were examined ultrastructurally, using a transmission electron microscope. Typical nondegenerating cells of various shapes with normal cytoplasmic organellae were seen. Degenerating and necrotic cells characterized by loss of normal organellae with vacuolations of the cytoplasm were in all sections studied. Icosahedral electron-dense particles (22 nm diameter) were in the degenerating and necrotic cells. The uniqueness of this finding is not known. The shape and size of the particles indicate that there may be viral involvement.