The importance of the RAS-BRAF-MEK-ERK signaling pathway due to mutations of BRAF in HCL and MAP2K1, encoding MEK, in SBLPN, led to the development of trials with BRAFi like vemurafenib, dabrafenib or encorafenib, and/or MEKi like trametinib or binimetinib in relapsed/refractory (R/R) HCL and HCL-like disorders. Here, MAPK1 is linked to hairy cell leukemia.