The Classification of Primary Cutaneous Malignant Melanoma

Abstract

A series of 60 primary cutaneous malignant melanomas was studied by serial block technique. The resulting 492 sections were classified as junctional nevus with or without atypia and preinvasive or invasive malignant melanoma according to Clark. No sections showed lentigo maligna (melanoma). The overall classification resulted in 49 superficial spreading malignant melanomas, 6 nodular malignant melanomas and 5 unclassifiable malignant melanomas. In 3 cases (5%) there was inconsistency between the classification of the central section and the overall classification of the tumor. Five theoretical growth patterns were postulated ranging from that of the pure superficial spreading malignant melanoma completely surrounded by a preinvasive area to the pure nodular malignant melanoma which completely lacks any such area. Borderline cases between these 2 types certainly seem to exist. Features such as intraepidermal Pagetoid growth of tumor cells, co-existence of a benign melanocytic component and histological indicating tumor regression were discussed. At least 3 tissue blocks should be taken from all malignant melanomas up to 25 mm in diameter and more if the tumor is larger.