Undifferentiated neuroectodermal tumors induced by human adenovirus type 31 in Syrian hamsters

Human adenovirus type 31 was inoculated intraperitoneally into 18 and intracranially into 98 Syrian hamsters within 24 hours of birth. Intraperitoneal tumors developed multicentrically in 94.4%, 93 days on an average after virus inoculation, while brain tumors developed in 6.1%, 154 days. Intraperitoneal tumors primarily developed in the subserosal tissues and protruded into the peritoneal cavity. Some of the five enlarged brain tumors seemed to have extended from the paraventricular regions to the neighboring structures, and one microtumor was located in the subependymal layer. Twenty-six of the 98 hamsters inoculated with virus intracranially unexpectedly developed tumors in the subcutaneous tissue of the skull. Histological, immunohistochemical and electron microscopic studies revealed that the tumors which developed in the different sites had essentially the same features and were composed of undifferentiated small cells of primitive neuroectodermal nature. The incidence and the characteristics of the tumors were discussed in comparison with those of adenovirus type 12-induced tumors described previously.