MAPK3 and mantle cell lymphoma: RAS-MAPK mutations are uncommon in MCL, with a few BRAF or NRAS mutated cases found by Nadeu and colleagues [9], one MAPK3 mutation found in a relapsed MCL case [10] and some KRAS, BRAF and NF1 mutations identified in a cohort of MCL patients who discontinued ibrutinib treatment [11].