Despite the still-widening list of prognostically significant genes, the only biomarker that influences the treatment strategy remains the presence of TP53 defects [98], and to date, there has not been enough evidence to support the use of NOTCH1, SF3B1, BIRC3 or ATM mutations, or CLL subclonal composition in making clinical decisions. The gene discussed is SF3B1; the disease is B-cell chronic lymphocytic leukemia.