Contributor: Gordon K. Klintworth
A xanthoma is a localized, benign self-limiting reactive lesion composed of lipid laden macrophages characterized by small, round nuclei and abundant foamy or finely granular cytoplasm which is rich in neutral lipid. A xanthoma is most often found in the subcutaneous tissue. Numerous types of xanthoma are recognized (histiocytosis X, Hand-Schüller-Christian disease, juvenile xanthogranuloma, Erdheim-Chester disease, xanthelasma, xanthogranuloma, eruptive xanthoma, tendon xanthoma [xanthoma - tendinous], xanthoma disseminatum, and xanthoma planum. Some xanthomas are associated with hypercholesterolemia. A xanthoma can occur in individuals with all subtypes of essential hyperlipidemia (especially hyperlipidemia type II and hyperlipidemia type III) and in persons with secondary hyperlipidemia [hyperlipidemia - secondary]. Many individuals with more than one xanthoma have normolipemia. Eruptive xanthomas are associated with hypertriglyceridemia as in diabetes mellitus. The typical xanthoma of the eyelid is the xanthelasma. Some types of xanthoma do not involve the eyelid (eruptive xanthoma, tendon xanthoma, and plane xanthoma).  Xanthoma rarely affects the orbit. Persons with juvenile xanthogranuloma usually has fewer skin lesions than those with xanthoma disseminatum and they tend to be self-limited. The lesions of juvenile xanthogranuloma progress for 1-2 years and then resolve spontaneously.