MAP2K1 and Langerhans cell histiocytosis: While CD1a+CD11c+CD14+CXCR4+ cells were detected in patients expressing BRAFV600E LCH-cells in situ (LCH6 and LCH9), we here report that circulating CD1a+CD11c+CD14+CXCR4+ cells were also detected in a patient who had lesional LCH-cells expressing a MAP2K1-mutation (LCH8).12