Characteristic histology of histiocytic lesions. Diagnostic biopsy specimens of LCH, JXD, and ECD lesions stained with hematoxylin and eosin. The LCH biopsy demonstrates characteristic clusters of histiocytes with reniform nuclei. The background inflammatory infiltrate includes lymphocytes, eosinophils, and macrophages. The JXG biopsy demonstrates characteristic xanthomatous histiocytes along with multinucleated Touton giant cells. The ECD biopsy is similar to JXG, also wth xanthomatous histiocytes and inflammatory infiltrate. (Images courtesy of Dr M. John Hicks, Baylor College of Medicine.)