Gastric cancer is the second leading cancer in Mongolia. Endoscopic submucosal dissection (ESD) of gastric cancer can only be curative if the cancer is detected at an early stage and a precise characterization of early gastric cancer is made on pathological diagnosis. Recent advances in targeted therapy give more successful treatment of choice for patients depending on their molecular characterization of the tumor.
We studied total 305 early gastric cancer cases, 198 ESD and 107 partial gastrectomy cases, between 2017-2019 at the National Cancer Center of Mongolia. Tumor subtype, LV invasion and tumor infiltrating lymphocytes (TIL) were assessed by optical microscopy, and verified by immunohistochemistry (IHC), Her-2 receptor evaluated by IHC and chromogenic in situ hybridization (CISH). EBV evaluated by IHC in high TIL cases.
All studied cases were adenocarcinomas. 66.6% (203/305) of the early gastric cancer was located in cardia. 28 cases (28/305) or 9.1% were positive for vascular invasion. High TIL observed in 51% (155/305) of cases. HER2 status was positive in 16% (50/305) by IHC. Among IHC her-2-negative cases her-2 gene expression detected in 11% (28/255) by CISH (Chromogenic in situ hybridization). 8.6% (9/105) of cases with high TIL were positive for EBV by IHC. Among ESD specimens 45% (90/198) were invasive adenocarcinomas and rest of them divided into high and low grade dysplasia.
Most common location of early gastric cancer was in cardia which is different from other high incidence countries like Japan and Korea. Her-2-positive cases were higher than other published studies. IHC-negative her-2 cases can have her-2 gene expression in CISH. There was a statistically significant relationship among TIL, tumor size, histological grade and LN metastasis.
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