Childhood pulmonary Langerhans cell histiocytosis: a comprehensive clinical-histopathological and BRAF mutation study from the French national cohort.

Childhood pulmonary Langerhans cell histiocytosis (PLCH) is a rare disease. Its pulmonary histopathology, according to comprehensive clinical-radiological findings and BRAF mutation status, has not yet been thoroughly documented. From the 167 childhood PLCH cases entered in the French National Histiocytosis Registry (1983-2016), we retrieved lung biopsies from a consecutive retrospective series of 17 patients, diagnosed when they were 2 weeks to 16 years old (median, 9.