Pediatric histiocytoses in the United States: Incidence and outcomes

Background Histiocytoses are rare disorders affecting the pediatric population. Materials and methods Surveillance, Epidemiology, and End Results database was searched for pediatric cases (<20 y old) of histiocytosis diagnosed between 1973 and 2010. Demographics, clinical characteristics, and survival outcomes were analyzed using standard statistical methods. Class I disease (Langerhans cell histiocytosis) and class III (malignant histiocytosis) were included in the data set. Results A total of 828 cases were identified. Overall incidence was 0.142/100,000 persons per annum. Incidence was highest in younger children and those of Asian or Native American descent. Class III disease had a higher incidence versus class I. Adolescents tended to present with class III, whereas young children presented with class I. Disseminated disease was present in most cases of class III, whereas class I had more localized cases. Surgical excision was more likely to be performed in class I. Overall median survival was 349 mo. Patients 15-19 y old and children <1 y old had the worst outcomes. Class I had higher survival compared with class III, which had a median survival of 33 mo. Cases with hematologic spread carried the worst prognosis. Surgical excision conferred a survival advantage while radiation had no effect. Survival improved over the study period. Gender and race had no association with survival. Conclusions Class I disease had localized cases and showed benefit from surgical intervention. Class III disease had a higher incidence and was associated with disseminated disease and lower survival. Radiation therapy did not affect survival. Overall survival increased over the previous 40 y.