Cutaneous malignant melanoma. Studies on the find structure of cells and their surface morphology in relation to tumour type and clinical course.

Cutaneous malignant melanoma occurs in three forms: lentigo maligna melanoma, superficially spreading melanoma, and nodular melanoma. The histology, the clinical development and the biological malignancy of these tumours differ. The purpose of the study reported here was to provide a clearer picture of the surface morphology of the malignant cells and to relate their fine structure to both the tumour type and the clinical development of the malignant melanoma. This investigation of 28 tumours from 22 patients of Scandinavian origin shows that at the electron microscope level there is no difference between malignant cells in the invasion nodulus of superficially spreading melanoma and nodular melanoma. The primary tumours were often built up of 2 or 3 differently differentiated cell clones. Metastases were built up of the same cells or cell clones that were found in the primary tumour. In several cases the surface of the malignant cells was folded, and covered with microvilli, microblebs and blebs. These surface alterations could be related in several cases to changes in the cytoskeleton of the cell (microtubuli and microfilament complexes). The clinical course of the malignant melanoma could best be correlated to the histogenetic type of tumour, depth of invasion, nucleus polymorphy and the quantity and arrangement of the microfilament complexes.