In accord with the molecular classification of gastric adenocarcinomas proposed by the TCGA44, we found a higher frequency (60%) of PIK3CA mutations in ctDNA of patients with Epstein–Barr virus (EBV)-positive (n = 3) or MSI-high tumors (n = 2) compared to the frequency (3%) in EBV-negative (n = 36) and MSS tumors (n = 37). This evidence concerns the gene PIK3CA and gastric adenocarcinoma.