Mucin phenotypic expression and background mucosa of esophagogastric junctional adenocarcinoma

In the West, the incidence of adenocarcinoma of the cardia or esophagogastric junction (EGJ) is increasing. This carcinoma is variously defined, however, and it contains heterogeneous tumors. In Japan, the frequency of this carcinoma is low, and little is known about it. We studied small esophagogastric junctional adenocarcinoma to determine its characteristics in Japanese patients.

Fifty-four patients with Siewert type II junctional adenocarcinoma (with tumors <<4 cm in maximum diameter) were studied. The carcinomas were classified into two types: tumors straddling the EGJ (EGJ-type) and tumors occurring entirely below the EGJ (bEGJ-type). Characteristics of the tumors and surrounding mucosae were evaluated. Phenotypic expression of mucin, p53 overexpression, and Helicobacter pylori infection were investigated histologically and immunohistochemically.

Twenty-three (43%) patients had EGJ-type and 31 (57%) had bEGJ-type carcinomas. The ratio of advanced cancers was significantly higher in EGJ-type. Some between-group similarities and differences existed in histological type, mucin phenotype, and p53 protein overexpression, but they were not statistically significant. In the mucosa surrounding EGJ-type tumors vs bEGJ-type tumors, oxyntic glands were significantly better preserved, gastric intestinal metaplasia occurred significantly less frequently, and the H. pylori infection rate was lower. Barrett's metaplasia was seen in only 2 patients, with the EGJ-type.

EGJ-type and bEGJ-type adenocarcinomas have different background mucosa of the stomach. EGJ-type has less atrophy of the oxyntic glands and less intestinal metaplasia in the stomach. This type appears to be the Western-type junctional adenocarcinoma that is still rare in Japan. Many cases of advanced junctional adenocarcinoma in Japan are of subjunctional origin.