Multinucleate cell angiohistiocytoma (MCAH) is an uncommon fibrohistiocytic disorder that usually presents as a localized solitary papule or multiple grouped papules. Generalized presentation is very rare with less than 20 cases reported in the literature. In this article, we present histopathological and immunohistochemical studies of 10 lesions from a patient with generalized MCAH. In all lesions, the histopathological changes were confined to a discrete zone of the superficial dermis that consisted of (1) an increase in the number of capillary-sized vessels with thickened walls, (2) presence of oval to dendritic spindle cells and stellate hyperchromatic multinucleated cells, (3) fibrosis marked by compact collagen, (4) hypertrophy and hyperplasia of small nerve fibers, and (5) a moderately dense lymphocytic infiltrate. The entire population of the cellular component including the multinucleated cells stained for CD10, whereas a subpopulation of the mononuclear spindle cells stained for factor XIIIa and CD68. CD34 highlighted only the blood vessels. The results confirm that the multinucleated cells lack expression of CD68 and factor XIIIa and that CD10 may be used to highlight the entire cellular component. The rarely reported hypertrophy and hyperplasia of nerve fibers in MCAH may be a common finding as it was observed in all 10 lesions.
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