OBJECTIVETo explore the clinicopathologic features, immunophenotype, differential diagnosis and gene mutation status of the Erdheim-Chester disease (ECD).

METHODSClinical and pathologic findings of 3 ECD cases were examined by gross, microscopic, immunohistochemical methods and BRAF V600E mutation. Related literatures were reviewed.

RESULTSTwo male patients and one female patient presented clinically with multiple skin nodules, bone pain and bony lesions by imaging study. Microscopically, the lesions were composed of spindle-shaped fibroblasts, foamy histiocytes and scattered Touton-type giant cells embedded in reactive fibrous tissue. Lymphocytes, plasma cells, and multinucleated giant cells were also found. Immunohistochemically, all histiocytes were positive for CD68, none of which expressed CD1a, although 2 cases focally expressed weak S-100 stain. In 2 cases,BRAF V600E mutation was detected.

CONCLUSIONSECD is a rare disease of xanthogranulomatous histiocytosis.Its diagnosis relies on pathological and immunohistochemical findings, but correlation with clinical information, especially radiographic findings should be performed.No effective treatment of the disease is currently available.