AECyTCL. Genes and pathways recurrently altered in AECyTCL. JAK2 and SH2B3, genes that govern the activation and termination of JAK2 signaling in normal hematopoietic cells, respectively, are mutually exclusively affected in 9 of 12 patients. The remaining 3 patients carry pathogenic indels/single nucleotide variations in other JAK-STAT pathway genes.