Gastric cancer with lymphoid stroma mimicking a subepithelial lesion after a 10-year disease-free interval: a case report

A 74-year-old male patient presented to our hospital for treatment of gastric cancer in 2021. He had previously visited our institution in 2011 for assessment of a gastric subepithelial lesion (SEL), which was discovered incidentally during a health screening esophagogastroduodenoscopy (EGD). Endoscopic ultrasonography and abdominal computed tomography were conducted for evaluation of the gastric SEL, revealing an approximately 1 cm lesion arising from the muscularis propria. The lesion was initially thought to represent a mesenchymal tumor such as leiomyoma or gastrointestinal stromal tumor. Owing to its small size and absence of symptoms, no immediate intervention was undertaken, and the patient underwent regular surveillance only. Follow-up was maintained until 2018 and no notable changes in the gastric SEL were detected. The patient then voluntarily discontinued further follow-up. In 2021, a routine health screening EGD identified changes in the gastric SEL, and histopathological analysis confirmed adenocarcinoma. The patient subsequently underwent radical total gastrectomy utilizing the Roux-en-Y technique, with the final pathological diagnosis being stage I (pT2N0M0) gastric cancer with lymphoid stroma (GCLS). As of April 2025, there has been no evidence of cancer recurrence. This case illustrates a lesion initially diagnosed as SEL that later was identified as GCLS after a 10-year interval. Therefore, during EGD, clinicians should consider the potential for SEL-like gastric cancer if an SEL is observed. This report highlights the importance of close monitoring and a thorough diagnostic evaluation.