The Histopathological Sequence in Viral Carcinogenesis in the Hamster Kidney2

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Abstract
The histogenesis of a very rapidly developing kidney tumor of hamsters was investigated by studying sections of the kidneys of hamsters killed on successive days after they received virus. A distinctive lesion was seen at 4 days; this developed in and was confined to mesenchymal cells that were sufficiently undifferentiated or embryonal to serve as precursors of both the medullary stroma and the musculature of the walls of arteries and veins of the arcuate system that were still developing. The lesion was manifested by extensive and simultaneous proliferative and degenerative changes in these cells. By 6 days intranuclear inclusion bodies were apparent. Subsequently the degenerative response to the virus became decreasingly obvious, but since the proliferative response continued, the histological picture changed from one characteristic of a virus infection to one typical of neoplasia. There was no evidence to suggest that the neoplasia represented anything but a continuance of the proliferative response that began before the 4th day in a multitude of cells distributed widely throughout the kidney. The similarity of the two types of responses elicited in stromal cells to those observed in lysogenic systems of bacteria, where a virus may either destroy its host cell or change its genetic nature, is pointed out, and the significance of the type of cell that became infected, and the speed with which this occurred, to the problem of why the newborn animal should be peculiarly susceptible to tumor virus, is discussed.