Retroperitoneal xanthogranuloma in a patient with Erdheim-Chester disease.

A case of Erdheim-Chester disease with retroperitoneal and renal sinus xanthogranuloma that occurred in a 50-year-old woman is presented. The 12 previously reported cases of Erdheim-Chester disease associated with retroperitoneal xanthogranuloma are reviewed and compared with 13 sporadic cases of retroperitoneal xanthogranuloma. Retroperitoneal xanthogranuloma is distinguished from inflammatory malignant fibrous histiocytoma by its lack of neutrophils, inconspicuous vascularity, lack of nuclear atypia, and abundant collagen. It is distinguished from inflammatory fibrosarcoma by its numerous foamy histiocytes, relative lack of plasma cells, and lack of nuclear atypia; it is distinguished from retroperitoneal fibrosis principally by its many foamy histiocytes, lack of plasma cells, and lack of vasculitis.