Tumour formation in hamsters inoculated with chick embryo lethal orphan virus

Department of Animal Pathology, University of Rhode Island, Kingston, Rhode Island 02881, U.S.A. Weanling hamsters were inoculated subcutaneously in the cheek pouch with tumour tissue, or dorsally with tumour tissue or tumour homogenate, obtained from tumours induced by chick embryo lethal orphan virus. Hamsters 1 to 3 days old were inoculated subcutaneously in the dorsal region with chick embryo lethal orphan virus. Females were found to be more susceptible to tumour induction and required a lower dose of virus. There was no evidence of increased tumour resistance in hamsters up to 3 days old. Most neoplasms developed between the sixth and eighth month, usually at the site of virus deposition, although a few were noted in the following 2 months. All hamsters inoculated with transplants via the cheek pouch developed neoplasms. This incidence was well above that for tumours induced in the dorsal area. All neoplasms were well encapsulated fibrosarcomas regardless of the size of the tumour and type or site of inoculation. Most tumours were ‘kidney-shaped’, multilobulated, and of soft consistency. * Present address: Union Carbide Research Institute, Molecular Biology Laboratory, Tarrytown Technical Center, Tarrytown, New York 10591. Present address: Department of Oncology, Rhode Island Hospital, Providence, Rhode Island 02903. Received 21 December 1970; accepted 4 June 1971.