Ultrastructural localization of alpha-3 integrin subunit in malignant melanoma and adjacent epidermis

Eight cases of malignant melanoma were studied by immunohistopathology and immunoelectron microscopy. alpha 3 integrin localization was documented in malignant melanoma cells, basal and suprabasal keratinocytes, melanocytes, blood vessels and in basement membrane material. In melanoma cell membranes and, to a lesser extent, the interior of melanosomal vesicles were labeled . In addition, neighbouring cells such as basal and suprabasal keratinocyte s and melanocytes showed strong alpha 3-integrin expression. The labeling w as much stronger in the plasma membrane than in the cytoplasm. Endothelial cells showed stronger labeling of the cytoplasm than of the plasma membrane . In some cases we found increased flocculent material surrounding melanoma cells or nests that seems to contain basement membrane protein components, specifically alpha 3-integrin subunits. Compared to normal epidermis alpha 3-labeling was stronger in tissues of malignant melanoma.