Malignant melanoma with melanosis. Ultrastructural and histological studies.

Ultrastructural and histological investigations were performed on a case of generalized melanosis associated with superficial spreading melanoma. The hyperpigmentation of the general body surface, mucous membranes and nail beds was associated with deposition of melanin in macrophages in the dermis, together with some hyperactivity of epidermal melanocytes. Melanin granules were observed lying free in the stroma, suggesting pigment incontinence and phagocytosis by macrophages. Giant melanosomes were noted in melanocytes, keratinocytes and melanophages in the hyperpigmented skin. No evidence was found to suggest dissemination of individual malignant cells throughout the skin. Subcutaneous nodules of malignant melanoma were, however, present, as well as metastases to the iris, liver and to other organs.