Consistent with the association of NOTCH1 mutations with clinically aggressive forms of the disease, B-CLL with NOTCH1 mutations at diagnosis have a poor prognosis similar to B-CLL carrying TP53 disruption and NOTCH1 mutations and TP53 disruption tended to distribute in a mutually exclusive pattern (44). Here, NOTCH1 is linked to B-cell chronic lymphocytic leukemia.