Mice develop hyperpigmented skin due to aberrant melanogenesis and melanocytic tumours develop but do not metastasizeThe transgenic line ‘304/B6’ (which has been back‐crossed to C57BL/6 for ten generations) spontaneously develops systemic skin melanosis, benign melanocytic tumours, and melanoma that undergoes metastasis to distant organsOn a background of Ednrb heterozygosity, these mice show late‐onset melanoma development with a high percentage of metastasis, and poor prognosis after tumour development. The gene discussed is EDNRB; the disease is melanoma.