Spontaneous tumors in the Dunkin-Hartley guinea pig

Seventy-nine spontaneous neoplasms in Dunkin-Hartley guinea pigs were observed over a 9-year period in the Fort Detrick guinea pig colony. Sixty-three of the neoplasms were found during approximately 8,500 necropsies performed on animals under 27 months of age. The remaining 16 tumors were in 34 breeders maintained after 27 months of age on a natural life-span study. Of this group, 10 (29.4%) developed neoplasms by the termination of the study, when the animals were 80 months of age. The skin tumor, trichofolliculoma, of which there were 29, comprised the largest tumor classification.