| A giemsa stain demonstrates numerous mast cells in the dermis in this case of urticaria pigmentosa, which is a form of localized mastocytosis seen most often in children. Lesions are often in groups, or may be solitary, and appear as brown pruritic papules. The mast cells contain numerous purple granules; the granules contain many substances, including vasoactive amines such as histamine, which are released upon activation and degranulation of the mast cells to cause the symptoms. A medium power view is seen below. |
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