CDKN2A and neoplasm: P531 and p16ink4a are the most common tumor suppressors lost in human cancer.2–6 We and others have shown that tumors with these mutations signal differently and, while this is well established in the world of basic research, it is not well appreciated by clinicians.7–9 It is well-known that certain cancer types have a large predominance of one type of tumor suppressor loss over another.