Biological and experimental consequences of the zonal composition of solid tumors.

The K-1735 melanoma is a transplantable murine tumor which, when growing s.c., is composed of melanotic and amelanotic areas. Results from trocar transplantation studies of tumor fragments show that expression of this phenotypic diversity can be terminated within very few passages. In parallel experiments, passage of cell suspensions derived from the whole tumor maintains this heterogeneity of melanin production. The implications of these findings are discussed.