CLL can be classified on the basis of several prognostic factors, including immunoglobulin heavy-chain variable (IGHV) mutation status; expression levels of CD38, ZAP70, and CLLU1; as well as somatic genomic abnormalities (trisomy 12, 13q14 deletion, 6q21 deletion, 11q23 deletion, 17p13 deletion, NOTCH1 mutation, and SF3B1 mutation). The gene discussed is NOTCH1; the disease is B-cell chronic lymphocytic leukemia.