Introduction

In 1950, the sixth revision of the ICD separated malignant melanoma (MM) of the skin from other forms of cutaneous cancer for the first time. Its clinical behavior is considerably more aggressive than the latter. The five-year survival rate is at best around 80% compared to virtually 100% for basal cell carcinoma.

Histology, classification and diagnosis

Malignant melanoma arises from the pigment-producing cells of the skin. Clinical diagnosis, which may not always be easy, is confirmed by histology. Approximately 70% of tumors probably arise in an existing pigmented nevus. The superficial spreading form constitutes around 60% of all malignant melanomas and is frequently indolent. Nodular melanoma (15%) grows rapidly being invasive ab initio. Lentigo malignant melanoma is very slow growing and occurs usually on the face of older persons and represents the most frequent of other forms. Prognosis is deduced from histological examination (Clark, 1969). Tumors less than 0.85 mm thick have a 90% five-year survival; over 4.65 mm a 40% five-year survival (Breslow, 1980).

The topographical distribution of malignant melanoma varies by sex, being commoner on the trunk in males and on the extremities in females.

Descriptive epidemiology

Incidence

The incidence of malignant melanoma of the skin varies by about 100 fold. Incidence is greatest in fair-skinned populations living in sunny climates, e.g. Hawaii, New Zealand. Rates in whites in Los Angeles and New Mexico are double those in New York State. The highest rates are in Australasia.