Variation in the incidence of renal adenocarcinoma among Rana pipiens held under tumor-promoting conditions

In 1975-1976, significant differences were observed in the frequencies of renal tumors in wild-caught frogs from different sites when they were held in the laboratory under tumor-promoting conditions. In 1979-1980, tumors could not be induced in frogs from a site where spontaneous tumors were no longer detectable. It is suggested that because spontaneous tumors have decreased in natural populations, it is less likely that the etiologic agent - the Lucke-tumor herpesvirus - will be present to promote tumor development under the stress of laboratory conditions.