NOTCH1 and B-cell chronic lymphocytic leukemia: Chromosomal rearrangements involving NOTCH1 t(7;9)(q34;q34.3) have been characterized in human T-ALL and lymphoma (7, 8), and NOTCH1 mutations have also been reported in 5.3–20% of chronic lymphocytic leukemia (CLL) (9, 10).