[Ultrastructural features of benign and malignant lesions of a melanocytic nature]

23 melanomas having the thickness, according to Breslow, up to 1.5 mm and 12 benign melanocytic tumours are studied. Ultrastructural examination gives additional information for differentiating benign and malignant melanocytic tumours. It is necessary to take into consideration such signs as the number and qualitative properties of melanosomes and premelanosomes, structure of nuclear membrane, that of nucleoli, non-specific microfilaments and mast cell infiltration of the tumour stroma. Some ultrastructural difference between lentigo-melanoma and other histological tumour types are noted.