Molecular Profiling of Tumor Tissue and Plasma Cell-Free DNA from Patients with Non-Langerhans Cell Histiocytosis.

The mutation and BRAF inhibitor responsiveness characterize ∼50% of patients with the non-Langerhans cell histiocytosis (non-LCH) Erdheim-Chester disease (ECD). We interrogated the non-LCH molecular landscape [ECD, = 35; Rosai-Dorfman disease (RDD), = 3; mixed ECD/RDD, = 1] using PCR and/or next-generation sequencing [tissue and cell-free DNA (cfDNA) of plasma and/or urine]. Of 34 evaluable patients, 17 (50%) had the mutation.