Extensive 0-IIc (undifferentiated carcinoma) lesion around a gastric adenoma: a case report.

A 73-year-old woman underwent esophagogastroduodenoscopy (EGD) at a local hospital, which revealed a flat elevated lesion, approximately 15 mm in diameter, in the posterior wall of the lower gastric body. At our hospital, a repeat EGD and biopsy led to a diagnosis of moderately dysplastic adenoma. The patient requested endoscopic submucosal dissection (ESD). Histopathology revealed a gastric adenoma with negativity for tumor at the vertical margin; however, the horizontal margin was positive for cancer with an undifferentiated carcinoma surrounding the adenoma. EGD was repeated, and a discolored area was found around the ESD scar. Biopsy revealed an undifferentiated carcinoma. Laparoscopic distal gastrectomy was performed, and postoperative histopathology also revealed an undifferentiated carcinoma (50 mm in diameter) surrounding the ESD scar; this lesion was an undifferentiated adenocarcinoma that was colocalized with and spread out to surround the original adenoma. This case is important for consideration of the pattern of development and progression of superficial spreading gastric cancer.