Supplementary Material for: Well-differentiated adenocarcinoma spreading widely in the gastric submucosa

A 56-year-old woman was referred to our hospital due to dry mouth. Diagnostic upper gastrointestinal endoscopy showed slightly elevated lesions both on the anterior wall and lesser curvature in the upper part of the stomach. Biopsy proven tuble-forming atypical cells in the two lesions led us to treat the presumed early gastric cancers with endoscopic submucosal dissection (ESD). Pathological examination of the ESD specimen showed well differentiated malignant cells spreading widely in the submucosa with positive lateral and deep margins. Retrospective image re-evaluation after ESD noticed us the correlation between the presumed early gastric cancers and the multiple submucosal cyst-like lesions in the gastric wall on computed tomography. Under the tentative diagnosis of gastric cancers originating not from orthotopic gastric mucosa but from submucosal ectopic gastric gland, the patient underwent laparoscopic total gastrectomy and regional lymph node dissection, revealing the tumor infiltration to the serosa and regional lymph node swelling. Post-operative pathological evaluation showed lymph node metastases, multiple submucosal cyst-like lesions lined with a single layer of presumably benign epithelium, papillary adenocarcinoma cells in the submucosa, and tubular adenocarcinoma cells both in the mucosal and subserosal regions. The patient was discharged on the postoperative 7th day without any events and completed adjuvant chemotherapy on an outpatient basis. General surgeons should note that cyst-like lesion(s) in the gastric wall might be a predictor of extensive submucosal cancer cell spreading even in a case of well differentiated gastric adenocarcinoma.