Objective To study clinicopathological features, diagnosis, differential diagnosis of oral Langerhans cell histiocytosis（LCH）, retrospective clinicopathologic study was carried on and a variety of immune phenotype were de -tected. Methods The clinicopathological features of 29 cases of oral LCH were analyzed. The immunohistochemical staining of S-100 protein, CD1a, CD83 and Ki-67 were used in above cases by immunohistochemical streptavidinbiotin peroxidase（SP） and Elivison two-step method. Statistical analysis was adopted for the results. Results Of the 29 cases of LCH, the expression of S-100 protein and CD1a were positive in 24 cases and negative in 5 cases, so 5 cases were excluded from the diagnosis of LCH. Among 24 cases of LCH, 15 patients were male and 9 were female. The median age was 7.50 years. 14 lesions were in the mandible, 5 were in the maxilla and 5 involved the mandible and maxilla. 9 cases were in stage Ⅰ, 13 in stage Ⅱ and 2 in stage Ⅲ, according to Bartnick classification. Immunohistochemistry showed all 24 cases staining for S-100 protein and CD1a were positive. Comparing with maxillofacial lesions involved soft tissue, Ki-67 positive rate was lower and CD83 positive rate was higher in maxillofacial single
bone lesion. Conclusion The immunohistochemical staining of S-100 protein and CD1a are important for the diagnosis
of LCH. Maxillofacial bone single LCH might have lower proliferative activity and a higher state of maturity. Maxillofacial
LCH involved soft tissue might have a higher proliferative activity and a lower state of maturity.
