With the introduction of these target molecules, it is crucial to well-stratify CLL patients with the aim of identifying those who can really benefit from a chemotherapy approach (e.g., immunoglobulin heavy chain variable region gene IGHV-mutated) and who cannot (e.g., tumor protein p53, TP53-mutated). The gene discussed is TP53; the disease is B-cell chronic lymphocytic leukemia.