Phagocytosis by mast cells in urticaria pigmentosa

Mast cells with endocytic and autophagic vacuoles were observed in a biopsy from a lesion of urticaria pigmentosa. In several areas of the specimen the mast cells revealed the typical morphology of mast cells which have released low molecular weight mediators, but this phenomenon did not seem to be correlated morphologically to the phagocytic activity of the mast cells. Some mast cells contained giant granules with a normal as well as an abnormal substructure.