Abstract
The influence of selective breeding on the incidence of cutaneous melanomas was studied in the Sinclair miniature swine melanoma model. Evaluation of the results of a large breeding study that produced 349 live progeny indicated that the incidence of melanomas (54%) was highest in newborn progeny derived from melanoma female Γ melanoma male (MF Γ MM) matings. Newborn progeny from normal female Γ melanoma male (NF Γ MM) and melanoma female Γ normal male (MF Γ NM) matings had incidences of 22% and 21% respectively; normal female Γ normal male (NF Γ NM) progeny had an incidence of 2%. Although most of the progeny were black, melanomas were observed in swine of various colors. Tumors occurred at differing cutaneous sites and did not demonstrate a predilection for any particular area of the body. During the first year of life, additional melanomas developed in some animals from all groups of progeny. At 1 year of age, the incidence of melanomas (85%) remained highest in MF Γ MM progeny. The incidence had increased to 57% and 50% in progeny from NF Γ MM and MF Γ NM matings while NF Γ NM progeny had an incidence of 4%. Although tumors were observed in newborn swine, most of the tumors (75.5%) developed after birth either from flat melanocytic lesions (19.3%) or from skin free of detectable melanocytic lesions (80.7%). An age effect was observed in tumor development; tumor development decreased as the age of the animals increased. These results demonstrate that selective breeding influences the incidence of melanomas in Sinclair swine and provide basic information required for further studies of tumor development, growth and regression in this unique spontaneous tumor system.