A retrospective histological study of 669 cases of primary cutaneous malignant melanoma in clinical stage I. I. Histological classification, sex and age of the patients, localization of tumour and prognosis.

A selected series of 669 primary malignant melanomas of the skin, stage I, has been classified according to Clark's system into lentigo maligna melanoma (86), superficial spreading malignant melanoma (259), nodular malignant melanoma (194) and unclassifiable malignant melanoma (130). It was often difficult to distinguish between lentigo maligna melanoma and superficial spreading malignant melanoma, and sometimes also between this last type and nodular melanoma. There seem to be borderline cases between the respective types. The 10-year specific cumulative survival rate (approximately the cure rate) was 98.3% for the lentigo maligna melanomas, 78.6% for nodular malignant melanomas and 76.7% for the unclassifiable group of melanomas. The 5-year observed prognosis ofthe 3 main types is satisfactory compared with other investigations. As the prognosis of the 3 types of cutaneous malignant melanoma differs considerably the use of this classification is recommended. The number of unclassifiable cases is likely to be reduced in the routine work when several sections of each tumour are studied.