What happened, in summary

A 53-year-old man was referred after routine endoscopy found a 15-mm gastric lesion that looked like a submucosal tumor. He had no abdominal symptoms. Endoscopic ultrasound suggested possibilities such as a neuroendocrine tumor or ectopic pancreas, and initial biopsies were negative for cancer. CT showed no enlarged lymph nodes or distant metastasis. He declined endoscopic removal and was lost to follow-up.

Three years later, screening endoscopy found the lesion again. It was similar in size, but the overlying lining had become red. Biopsies were still negative. About a year after that, he returned with mild indigestion. The lesion had enlarged to about 18 mm and developed a small central ulcer. This time biopsy showed high-grade dysplasia.

He agreed to endoscopic submucosal dissection. Pathology of the removed lesion unexpectedly showed moderately differentiated gastric adenocarcinoma with only shallow invasion into the submucosa and no lymphovascular invasion. His recovery was uncomplicated. He continued outpatient surveillance, and over 4 years of follow-up there was no evidence of local or distant recurrence. The case shows how an early gastric cancer can mimic a non-cancerous submucosal mass for years.