CDKN2A and esophageal squamous cell carcinoma: CDKN2A loss occurred in 41 ESCC formalin-fixed and paraffin-embedded (FFPE) samples (25%, 41/161), while CDKN2B loss was detected in 21 samples (13%, 21/161), with loss of both being found in 18 samples (11%, 18/161) (Supplementary Fig. 5a).