Mast cells containing melanin granules in sublingual keratosis

In an ultrastructural study of 3 biopsies taken from the floor of the mouth of 2 patients suffering from sublingual keratosis, it was found that some of the mast cells appearing within the epithelium and connective tissue contained melanin granules which were found to be positive with Masson Fontana stain for melanin. These cells showed all the characteristic features of mast cells and not macrophages. The present results suggest that mast cells have phagocytosed melanin granules and therefore support those views suggesting that mast cells are capable of phagocytosis. They also suggest that not all the cells containing melanin granules and appearing in the lamina propria are the conventional melanophages but some of these may be mast cells.