2025 Volume 67 Issue 6 Pages 1168-1174
A 62-year-old woman presented to our hospital with a gastric tumor. EGD showed a 2-cm submucosal tumor with central ulceration on the anterior side of the gastric antrum. Signet ring cell carcinoma and poorly differentiated adenocarcinoma (PDA) were detected by endoscopic biopsy; Helicobacter pylori (H. pylori)serum antibody and urease breath test were negative.
Distal gastrectomy was performed with D2 lymph node dissection. Macroscopically, the tumor was 2.0×1.2 cm in size with submucosal tumor-like appearance. Microscopically, signet ring cell carcinoma was present only in the mucosal layer. PDA with high proliferative activity was present with fibrous tissue proliferation mainly in the submucosal layer, and invaded the proper muscular layer. The PDA pushed up the signet ring cell carcinoma and non-neoplastic mucosa. In Japan, only four cases of H. pylori-naive undifferentiated-type gastric cancer invading the proper muscular layer have been reported, including this case. Further accumulation of such cases is required.
