Embryonal neuroepithelial tumors induced by human adenovirus type 12 in rodents. 1. Tumor induction in the peripheral nervous system.

Human adenovirus type 12 (Ad 12) was inoculated intraperitoneally, intrapleurally, intramuscularly or subcutaneously into newborn rodents. Tumors developed preferentially in the peritoneal cavities in 93.9% of the hamsters and 82.6% of the mice, but none in rats; in contrast to the high incidence of brain tumors in rats when the virus is injected intracranially. Serial section of peritoneal tissues and muscle of hamsters revealed multicentric microtumors with a close relation to peripheral nerve fibers 10 to 35 days after virus inoculation. Histologically, most tumors consisted of closely packed, irregularly arranged, small spindle or tadpole-shaped cells. However, divergent morphological differentiation showing palisade arrangement of spongioblastic tumor cells forming trabeculae, pseudorosettes with or without central blood vessel, and true rosettes of immature ependymal (ependymoblastic) or medulloepithelial type were observed. No further differentiation was detected on immunohistochemical or electron microscopical examination of the tumor cells. The immature neuroepithelial phenotypes and the early stages of tumor development indicated that Ad 12 had a definite affinity for embryonic neuroepithelial elements that have migrated along the peripheral nerve fibers of newborn hamsters and mice, perhaps with cells of neural crest origin, and had induced primitive neuroectodermal tumors as observed in human peripheral neuroepithelioma and medulloepithelioma.