In line with this hypothesis, mutations in several genes other than STAT3 and STAT5B involved in this JAK/STAT signaling pathway, such as the IGSF3, JAK3, PTPRT, TTN, and USH2A genes, have also been sporadically reported in LGLL [25,27,28,54]. The gene discussed is IGSF3; the disease is T-cell large granular lymphocyte leukemia.