Clinical Pathology Study:between Erdheim-Chester Disease And Other Histiocytic Tumors

Objectives Exploring the clinicopathological features, immunophenotype, differential diagnosis and gene mutation status of the Erdheim-Chester disease by immunohistochemical and molecular biology. Comparing Erdheim-Chester disease with other histiocytic tumors.Methods Clinical and pathologic findings of 24 cases of the Erdheim-Chester disease retrieved from the archives of Peking Union Medical College Hospital were examined for microscopic, immunohistochemitry findings, and BRAF V600E mutation. Clinical and pathologic findings of 41 cases of the Langerhans cell histiocytosis(LCH),15 cases of the follicular dendritic cell sarcoma(FDCS),2 cases of the interdigitating dendritic cell sarcoma(IDCS),5 cases of the histiocytic sarcoma(HS),7 cases of the inflammatory pseudotumour-like FDC sarcoma(IPT-FDCS) were examined for microscopic, immunohistochemitry findings, and BRAF V600E mutation.Results The mean age of the patients was 39 years (range 4-63). Erdheim-Chester disease has a wide range of involvement, most of them (83%) involved long bone. The half of patients have other infiltration, the main sites of involvement included skin, orbital and periorbital, hypothalamic-pituitary axis, heart, kidneys, nervous system, after the peritoneal cavity, liver, spleen, skeletal muscle, adrenal gland. Immunohistochemically, all the histiocytes were positive for CD68, none of them expressed CDla, while some cases weakly expressed S-100 focally. BRAFV600Emutation was detected in 54.3% patients. Langerhans cell histiocytosis were positive for CD68 and CDla. BRAFV600Emutation was detected in 22.0% patients. Follicular dendritic cell sar-coma were positive for CD68, CD21 and CD35. BRAFv600E mutation was detected in 6.7% patients. Interdigitating dendritic cell sarcoma were positive for CD68, S100 and Vimentin, negative for CD21 and CD35. Ki-67 labeling index was 15%. BRAFV600E mutation was detected in 50% patients. Histiocytic sarcoma were positive for CD68, EMA, locally positive for S100, negative for CD21, CD35, CDla, Ki-67 labeling index was 50%. BRAFV600E mutation was not detected in the patients. Inflammatory pseudotumour-like FDC sarcoma were positive for CD21, CD3, CD23, SMA. EB virus situ hybridization was positive. BRAFV600Emutation was not detected in the patients.Conclusion Erdheim-Chester disease is a rare xanthogranulomatous histiocytosis. The diagnosis relies on pathological and immunohistochemical findings, BRAFv600E mutation was detected with high positive rate, but clinical information, especially radiographic findings must be thoroughly integrated. It has not been very effective in the treatment of the disease. The other histiocytic tumors don’t have the fiber xanthogranulomatous histologic features. There are separate histological and immunohistochemical expression characteristics in the other histiocytic tumors. BRAFV600E mutation was detected with low positive rate.