biostudies-literatureUnknown11(2)Teran E<h4>Background</h4>Claudin 18.2 (CLDN18.2) is highly expressed in up to 40% of gastroesophageal adenocarcinomas (GEA) and represents an emerging therapeutic target for these tumors. However, its distribution across molecular subtypes and its prognostic and predictive roles remain insufficiently studied.<h4>Methods</h4>This ambispective, multicenter study included 563 patients with GEA diagnosed between 2019 and 2025 across 17 European institutions. Tumor samples were analyzed for CLDN18.2, human epidermal growth factor receptor 2 (HER2), mismatch repair, Epstein-Barr virus (EBV), and programmed death-ligand 1 [PD-L1; combined positive score (CPS)] using immunohistochemistry and/or in situ hybridization. Molecular alterations were characterized using next-generation sequencing. AssociationsESMO open106053https://www.ebi.ac.uk/biostudies/studies/S-EPMC12865641biostudies-literatureClaudin 18.2 expression in gastroesophageal adenocarcinoma: biomarker overlap and association with clinical outcomes in a European cohort.PMC12865641Elez EAlsina MTeran EAgra CFoti SBlanco CReboredo MVivancos AMacarulla TZucchiatti ALopez AAcosta DGarcia-Paredes BTian TVSauri TFornaro LTabernero JLandolfi SMacias IPazo RAles IGenovesi VMartinez JVisa LHerranz JMVidal-Tocino RHierro CRibera PCalvo ABuges CMartinez ECarita LfalseClaudin 18.2 expression in gastroesophageal adenocarcinoma: biomarker overlap and association with clinical outcomes in a European cohort.<h4>Background</h4>Claudin 18.2 (CLDN18.2) is highly expressed in up to 40% of gastroesophageal adenocarcinomas (GEA) and represents an emerging therapeutic target for these tumors. However, its distribution across molecular subtypes and its prognostic and predictive roles remain insufficiently studied.<h4>Methods</h4>This ambispective, multicenter study included 563 patients with GEA diagnosed between 2019 and 2025 across 17 European institutions. Tumor samples were analyzed for CLDN18.2, human epidermal growth factor receptor 2 (HER2), mismatch repair, Epstein-Barr virus (EBV), and programmed death-ligand 1 [PD-L1; combined positive score (CPS)] using immunohistochemistry and/or in situ hybridization. Molecular alterations were characterized using next-generation sequencing. Associations2026-01-01T00:00:00Z2026 Jan2026-07-15T06:38:16.625Z2026-07-02T03:08:43.469ZS-EPMC128656414160481910.1016/j.esmoop.2025.106053