A 20-year-old female underwent an endoscopy for epigastralgia that revealed many small, elevated nodules in the antrum that were diagnosed as nodular gastritis. The endoscopy also showed an ulcerative lesion with an uneven round wall at the greater curvature of the middle corpus. Biopsy of the ulcerative lesion yielded a diagnosis of poorly differentiated adenocarcinoma. A distal gastrectomy was performed on the basis of a diagnosis of gastric cancer associated with nodular gastritis. The intraoperative findings revealed serosal invasion of the gastric cancer and the patient tested positive for peritoneal cytology. The pathological findings revealed poorly differentiated adenocarcinoma showing invasive growth with fibrosis on the corpus and large and superficial lymphoid follicles on the miliary nodules at the antrum. The patient was positive for Helicobacter pylori infection by both the serum Helicobacter pylori antibody and histopathological findings.