Collectively, these three studies identified the following six risk factors for RT: lymph node size ≥3 cm, various abnormal CLL FISH patterns (see below), mutational status and stereotypic pattern of the immunoglobulin heavy chain variable region (IGHV), TP53 disruptions (mutations and or deletions), NOTCH1 mutations and complex karyotype (CK, defined as ≥3 chromosomal abnormalities within the same clone) (Table 1). Here, NOTCH1 is linked to B-cell chronic lymphocytic leukemia.