Inheritance of malignant melanoma in the melim strain of miniature pigs

Abstract

Selective breeding of miniature pigs bearing cutaneous tumours resulted in the establishment of the MeLiM strain with hereditary malignant melanoma. The inheritance of melanoma was tested in a two-generation kindred comprising 456 progeny from 78 litters. Melanomas were recognisable visually as black-pigmented lesions on the skin. Their size, shape, number, progression and metastatic spreading varied widely. All possible melanoma forms known in human melanoma, i.e. pigmented naevi, dysplastic naevi, superficial spreading melanoma and nodular malignant melanoma, were found in the MeLiM pigs. Because the occurrence of nodular malignant melanoma segregated in all recorded litters we have included only this form in the genetic analysis. The tumours were nodular with exophytic growth over the skin surface. All showed similar histopathological features, vertical growth to muscle fascia and high metastatic activity. We hypothesize, on the basis of segregation ratios obtained from various mating types, that the mode of inheritance of nodular melanoma in the MeLiM strain is probably controlled by three genes.