Viral-induced astrocytomas in squirrel monkeys.

Saimiri sciureus, the squirrel monkey, is susceptible to the oncogenic effects of JCV following intracerebral inoculation. As in owl monkeys, tumor development follows an incubation time of 14 to 30 months. Four of six virus-inoculated monkeys developed cerebral tumors, three of which were astrocytomas grade 4 and the remaining tumor was a poorly differentiated astrocytoma. All tumors showed high cellularity, mitotic figures, and cellular pleomorphism. In the astrocytoma grade 4, neovascularization was a prominent feature. The blood vessels in the poorly differentiated astrocytoma appeared normal. Multinucleated giant cells were present in all four astrocytomas. Antemortem hemorrhage was seen in one astrocytoma grade 4. Other tumor types were not seen. The occurrence of astrocytomas in a second species of New World monkeys confirms the oncogenicity of JCV for nonhuman primates.