Necrobiosis in solitary mastocytoma: coincidence or pathogenesis?

The coexistence of solitary mastocytoma and necrobiotic changes resembling granuloma annulare in the same lesion has not been reported to our knowledge. A 3 1/2-year-old child with a plaque on the arm clinically and histologically consistent with solitary mastocytoma showed characteristic necrobiotic foci indistinguishable from granuloma annulare. We speculate that mast cell degranulation may be involved in the pathogenesis of necrobiosis by altering fibroblast enzyme activity and/or producing prolonged inflammatory reactions.