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The Nature of the Hemorrhagic Lesions Induced by Polyoma Virus in Hamsters^*

Vittorio Defendi and John M. Lehman

(The Wistar Institute of Anatomy and Biology, Philadelphia, Pa.)

Hemorrhagic lesions induced by polyoma virus in newborn or adult hamsters have been microscopically analyzed. There was no evidence of endothelial necrosis, but the most characteristic feature was proliferation of endothelial cells. Emboli of liver and tumor cells occurred frequently in the lung, even though the possibility of primary tumors in this organ could not be excluded. Nine out of 22 liver hemangioendotheliomas (eight from young animals and one from an adult) and five out of twelve lung lesions (four from young animals and one from an adult) could be successfully grafted in adult animals that were not preconditioned. Eight out of nine tumors have been serially transplanted and are now between the eighth and thirteenth transfer. These tumors present the histological picture of a hemangiosarcoma accompanied by active mesenchymal tissue proliferation, probably of host origin, with capillary angiomas, monocytic cell infiltration, and hemosiderin deposition. Some of the transplantable tumors gave a high incidence of metastasis. The possibility that these tumors could be induced de novo by possible virus present in them can be safely excluded on the basis of experiments with filtrates from these tumors. A 4-dimethyl-aminoazobenzene-induced transplantable hemangiosarcoma has also been analyzed for comparison.

Some of the features common both to these transplantable hemangiosarcomas in the hamster and Kaposi's sarcoma in man have been described.

^* This work was supported, in part, by U.S.P.H.S. Research Grant CA-04534 from the National Cancer Institute and by Grants E-88 and E-89 from the American Cancer Society.

Leukemia Society Scholar.

Received 10/ 7/63.