BRAF Mutations in Pulmonary Langerhans Cell Histiocytosis: A Multicentre Survey

Pulmonary Langerhans cell histiocytosis (PLCH) is a smokingrelated condition in which aggregates of Langerhans cells admixed with other inflammatory cells are found in lung tissue. The general view is that PLCH is a reactive condition rather than a neoplasm. However, in small series BRAF c.1799T>A (p.V600E) mutations have been identified which raise the possibility that PLCH may have features of a neoplasm after all. Because the reported cases are few in number, we undertook a multi-institute survey of BRAF mutations in adult smokers. We found BRAF V600E mutations in 57% of our cohort of 61 patients. No significant relation with age or gender and BRAF status was found. Our series confirms the presence of BRAF V600E mutations in a large proportion of PLCH patients.