Amplification of the JAK2 locus has been described in Hodgkin disease and
mediastinal B - cell lymphoma, 18,19 and biallelic inactivating mutations in suppressor of cytokine signaling - 1 (SOCS - 1), a negative regulator of JAK2, have been identified in
mediastinal B - cell lymphoma.20 Genomic analysis of JAK2 and of other JAK - STAT pathway members may lead to the identification of mutations of the JAK - STAT pathway in lymphoid diseases and other malignancies.