JAK1 and T-cell prolymphocytic leukemia: JAK1 mutations have been found in adult precursor T acute lymphoblastic leukemia (ATLL, 18%) [6], T-cell prolymphocytic leukemia (T-PLL, V658F, responding well to JAK1-inhibition therapy) [7], cutaneous T-cell lymphoma (CTCL) [8], anaplastic large cell lymphoma (ALCL, 18%) [9,10], plasmablastic lymphoma (PBL,14%) [11], peripheral T-cell lymphoma (PTCL, G1097D) [12] and enteropathy-associated T cell lymphoma (EATL) [13].