NOTCH1 and B-cell chronic lymphocytic leukemia: Richter transformation is a severe complication in the course of CLL, characterized clinically by rapidly enlarging lymph nodes, B symptoms (such as fever, night sweats, and weight loss), and abnormal laboratory parameters, and molecularly by mutations in TP53, NOTCH1, MYC, and complex chromosomal abnormalities, with high aggressiveness and poor prognosis (27).