STAT5B and neoplasm: There were three assigned cohorts: tumor identified with activating mutations in JAK1, JAK2, JAK3, STAT3, or STAT5B; patients lacking in these factors but with functional evidence of JAK/STAT activation determined by ≥30% pSTAT3 staining in tumor cells; and patients who did not fit into cohort 1 and 2, or who lacked adequate tissue suitable for IHC stain.