Rapidly Growing Papillary Well-Differentiated Adenocarcinoma in a Patient With a Helicobacter pylori-Naive Gastric Mucosa

Although undifferentiated adenocarcinomas and fundic gland-type carcinomas are known as Helicobacter pylori-naive gastric carcinomas, well-differentiated gastric phenotype adenocarcinomas with papillary growth are rare. We encountered a case of a rapidly growing pedunculated well-differentiated adenocarcinoma in a patient with a H. pylori-naive gastric mucosa. The tumor had characteristics of a gastric phenotype (pepsinogen I and H and K-adenosine triphosphatase staining negative; diffusely positive for both mucin-5AC [MUC-5AC] and MUC-6; and MUC-2, common acute lymphocytic leukemia antigen 10 [CD-10], and p53 negative) and treated with endoscopic mucosal resection. We report our case along with a relevant literature review.