THE INTRA‐LESIONAL VARIATION OF TYPE, LEVEL OF INVASION, AND TUMOUR THICKNESS OF PRIMARY CUTANEOUS MALIGNANT MELANOMA

Abstract

In order to evaluate the prognostic importance of type of melanoma, level of invasion and tumor thickness in a retrospective study of cutaneous melanomas, it is prerequisite that the available histological material be representative. To investigate this condition 55 primary cutaneous melanomas were studied randomly by serial block technique. The histological classification of each tissue block as to type of melanoma, level of invasion and tumor thickness was correlated with the overall classification of the corresponding whole tumor. The typing included 6 groups: superficial spreading melanoma, lentigo maligna melanoma, nodular melanoma, acral lentiginous melanoma, melanoma of unclassifiable type and nevoid lesion. The depth of tumor invasion was graded by 5 levels. The tumor thickness was measured in mm as described by Breslow, and arranged in 6 groups (0-0.75 mm, 0.76-1.50 mm, 1.51-2.25 mm, 2.26-3.00 mm, 3.01-6.00 mm and > 6.00 mm). The study revealed a consistency of 95% (52/55) between the type of the central cross section and the type of the whole tumor. In 96% (53/55) of the central cross sections the level of invasion was equal to that of the whole tumor. In 95% (52/55) of the central cross sections the tumor thickness was situated in the same group as that of the whole tumor. Type, level and thickness of malignant melanomas can be evaluated in retrospective studies if central cross sections of the melanomas are available for histological examination.