PROGNOSTIC IMPORTANCE OF MOLECULAR-LIKE CLASSIFICATION IN GASTROESOPHAGEAL JUNCTION TUMORS (IZMIR ONCOLOGY GROUP [IZOG] STUDY)

A comprehensive molecular classification was published in 2014 within The Can-cer Genome Atlas (TCGA) to guide clinical approaches and treatment strategies. This study aimed to investigate the clinicopathological and prognostic impor-tance of the classification using immunohistochemistry (IHC) and chromogenic in situ hybridization (CISH) to identify potential surrogate markers of molecular changes in gastroesophageal junction (GEJ) adenocarcinomas. A total of 52 GEJ adenocarcinomas were divided into five groups using IHC with MLH-1, E-cadherin, p53 and CISH with EBER: 1) microsatellite unstable (MSI: negative with MLH-1), 2) genomically stable tumors (GS: positive with p53), 3) chromosomally unstable tumors (CUN: negative with e-cadherin), 4) EBV+ tumors (EBV+: positive with EBER) and 5) unclassifiable (G-NOS: MLH-1 and e-cadherin positive with p53 and negative with EBER). The largest group consisted of 24 (46.2%) cases of CUN tumors. This group was followed by groups of GS with 14 (26.9%) cases, MSI with 7 (13.5%) cases, and EBV + with 3 (5.8%) cases, respectively. Although this classification was not as-sociated with pathological features, it was found to be closely related to prognosis (p = 0.029). Patients with EBV+ tumors had the longest overall survival, followed by the G-NOS, MSI, CUN, GS groups.