Biological behaviour of cutaneous malignant melanomas

The classification proposed by Clark et al. of cutaneous malignant melanoma into 3 groups: lentigo maligna melanoma (LMM), superficial spreading melanoma (SSM) and nodular melanoma (NM) was based on a correlation between histology and biological behaviour. Many studies have shown different growth rates, prognosis and incidence of antecedent benign nevi for each of these groups, confirming that each is a separate entity with its own biological behaviour. The recent proposal that acral lentiginous melanoma (ALM) is a distinct clinico-histological entity, however, is more difficult to accept. Many melanomas on acral locations are histologically intermediate between SSM and ALM and the epidemiological value of classifying ALM as an entity separate from SSM is doubtful.