The top 10 most frequently mutated genes among 64 gastric PC GC patients were TP53 (48%), CDH1 (31%), ARID1A (14%), FGFR2 (14%), CDKN2A (9%), ERBB2 (9%), LRP1B (9%), FGF19 (8%), FGF3 (8%), and FGF4 (8%), compared to TP53 (66%), ARID1A (20%), LRP1B (16%), CDH1 (14%), PIK3CA (12%), FAT4 (10%), TGFBR2 (10%), KRAS (10%), APC (9%) and KMT2D (8%) in non-PC GC patients (Fig. 1a). The gene discussed is PIK3CA; the disease is pachyonychia congenita.