Abnormalities affecting more downstream signaling pathways are prominent in certain PTCLs, such as JAK/STAT3 signaling in anaplastic large cell lymphoma (ALCL) and STAT5B mutations in monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL) and hepatosplenic T-cell lymphoma (HSTCL). This evidence concerns the gene STAT5B and hepatosplenic T-cell lymphoma.