Answer: Juvenile xanthogranuloma

Histology: Beneath a normal epidermis one sees a collection of foamy histiocytes and giant cells with a wreath-like configuration of nuclei.

Discussion: Juvenile Xanthogranuloma (JXG) is a benign histiocytic lesion that usually occurs in childhood and presents as a reddish-brown papule involving the head and neck area, but other sites can be involved. Multiple lesions may be associated with neurofibromatosis and juvenile chronic myelogenous leukemia. Visceral involvement may occur, but this is rare. Histologically, one typically sees a well circumscribed dome shaped lesion in the superficial dermis consisting of foamy histiocytes and giant cells that have nuclei in a wreath configuration (Touton giant cells). Neutrophils, lymphocytes, and eosinophils may be interspersed throughout the lesion.

Necrobiotic xanthogranuloma (NXG) may show Touton like giant cells, but one usually sees striking necrobiotic change throughout the dermis associated with extracellular cholesterol deposits. NXG typically presents in adults and is associated with monoclonal gammopathy. Xanthomas have foamy histiocytes, but lack Touton giant cells. Although dermatofibromas may have xanthomatized histiocytes, they usually have the characteristic collagen wrapping configuration associated with peudoepitheliomatous hyperplasia and basal layer hyperpigmentation.