Images in Allergy and Immunology

摘要

Mastocytomas in children are usually cutaneous lesions (urticaria pigmentosa) that consist of solitary brown-tan plaques or nodules larger than 1 cm, typically located on the skin of the extremities, face, scalp, and trunk but not of the palms or soles. Rubbing or stroking of the lesions induces urtication (Darier's sign). Association with systemic mastocytosis is rare, and serum tryptase levels are normal. They rarely bleed and typically resolve at puberty. Extracutaneous mastocytomas (Fig 1) are rare and of unknown prognosis. Perivascular accumulation of scroll-poor, tryptase- and chymase-positive mast cells with spindle shape or spherical forms are characteristic (Figs 2-6). The differential diagnosis includes malignant melanoma, histiocytoma, eosinophilic granuloma, Kaposi sarcoma, and basal cell carcinoma. Specific stains for tryptase, chymase, and chloroacetate esterase can lead to the diagnosis because poorly granulated mast cells stained with Giemsa or toluidine blue stains can be mistaken for eosinophils or histiocytes.