CD19 and hairy cell leukemia: A panel of pan-B cell markers and antigens commonly expressed on hairy cells (CD19, CD20, CD22, CD103, CD11c, CD123 and CD25) is used to diagnose HCL cells.1–4 Annexin A1, which is not expressed in any other small B-cell lymphoproliferation, is currently the most specific HCL marker.1,5 Tiacci et al have identified BRAF-V600E mutation as the disease-defining genetic event among patients with classical HCL.6,7