Herein we describe two cases of advanced gastroesophageal and gastric adenocarcinomas characterized by aggressive disease course, rapid progression despite standard first-line chemoimmunotherapy, and the presence of high-level FGFR2 amplification with concurrent WDR11-AS1–FGFR2 fusion detected by circulating tumor DNA (ctDNA) analysis. This evidence concerns the gene FGFR2 and neoplasm.