Incidentally Diagnosed Very Well-Differentiated Gastric Adenocarcinoma at Intraoperative Frozen Section.

Very well-differentiated gastric adenocarcinoma is a rare subtype that is often overlooked because of minimal cytological atypia and ill-defined gross findings. We report an 82-year-old man who was incidentally diagnosed with this entity in an intraoperative cut-end frozen section during gastrectomy for another adenocarcinoma. The frozen specimen showed irregularly fused glands with characteristic architecture, prompting additional resection to secure negative margins. Immunohistochemistry revealed loss of AT-rich interaction domain 1A expression exclusively in the neoplastic glands. This case highlights the importance of recognizing subtle architectural abnormalities in frozen sections to avoid overlooking clinically undetected gastric neoplasms.