Gastric Clear Cell Adenocarcinoma Derived from Papillary Adenocarcinoma and its Molecular Alterations

Introduction: Although clear cell carcinoma has been reported in the gastrointestinal tract, such as the colon, clear cell adenocarcinoma (CCA) is a rare histological variant of gastric adenocarcinoma. It may be important for pathologists to distinguish CCA from clear cell metastatic lesions arising from other organs, especially the kidney. Even more importantly, the molecular alterations occurring in CCA should be identified. Case Report: Here, we present a rare case of gastric CCA with a papillary adenocarcinoma (PA) component and evaluated the molecular alterations in the CCA (submucosal lesion) and PA (intramucosal lesion) components separately. MUC2, MUC5AC, MUC6, and CD10 expression was observed immunohistochemically in both components. According to the findings, the phenotype was considered the gastric and intestinal phenotypes (mixed type). Although CDX2 was diffusely expressed in the PA component, its expression was more sporadic in the CCA component. Using a customized gene panel, p53 was overexpressed in both components, suggesting mutation of TP53 (P152L (cCg>cTg) in exon 5, missense mutation). Conclusions: Although the specific molecular profile of gastric CCA was not identified in the present case, gastric CCA is a unique histological variant of gastric cancer in terms of the clinicopathological findings. Word count, 193.