CDKN2A and head and neck squamous cell carcinoma: In terms of the proportions, the five most common somatic copy number (SCN)-altered genes in HNSCC were CDKN2A (deleted in 32.03% of patients), CDKN2B (deleted, 28.34%), PPFIA1 (amplified, 26.02%), FADD (amplified, 25.63%) and ANO1 (amplified, 25.44%).