Adenovirus 12-induced tumor has been so far considered to be an undifferentiated sarcoma, but in the present study it has been possible to obtain such electronmicroscopic findings that substantiate well the theory of the neuro-ectodermal supporting cell origin as suggested by the observation at optical level. In other words, a specific clinging picture of cellular membranes and the presence of desmosomes have been demonstrated. In addition, though only in rare instances, the presence of virus-like particles have been verified, and some comments
have been made about the relation between tumor and the appearance of virus as well as about carcinogenic mother cell.</p
