Transformation From Oxyntic Gland Neoplasm Into Advanced Gastric Cancer via TP53 Mutation: A First Case Report.

The molecular genetic mechanisms behind oxyntic gland neoplasm (OGN) progression are not well established. We present the first case suggesting that a TP53 mutation caused the transformation from OGN into advanced gastric cancer with nodal metastasis. An 80-year-old man presented with anemia and was found to have a gastric tumor measuring 35 × 30 mm. Histology revealed predominantly invasive tubular adenocarcinoma showing diffuse p53 positivity, with a minor chief cell-predominant OGN component. Targeted sequencing of the entire tumor revealed a pathogenic TP53 c.832C>A (p.Pro278Thr) mutation; no mutations were found in GNAS or KRAS. A double stain (p53/MUC5AC) provided immunohistochemical evidence of a shift from wild-type to mutant-type p53 expression, particularly in the foveolar epithelium within the intramucosal OGN component, suggesting the acquisition of a TP53 mutation during tumor progression. This case supports an unreported role for TP53 in the transformation of OGNs into aggressive carcinomas.