Epithelial Dysplasia and Adenomas
In the stomach, the term “adenoma” is used to describe polypoid dysplasia that does not fit into one of the other named polyp categories (ie, a recognizable fundic gland polyp with superimposed dysplasia would not technically be deemed an adenoma). In places where gastric cancer is common (such as East Asia), gastric adenomas are common as well. Here in the United States, we rarely encounter adenomas in biopsies from the stomach. By definition, an adenoma should appear as a polyp or nodule endoscopically. Most adenomas that we do encounter contain dysplastic intestinal-type epithelium. Rarer subtypes harbor dysplastic foveolar-type epithelium (so-called “type II” dysplasia) or are composed of pyloric gland-like structures. These polyps can contain low-grade or high-grade dysplasia, and must be carefully searched for evidence of an early adenocarcinoma invading the lamina propria (“intramucosal adenocarcinoma;” see Chap. 25). In the West, we use a two-tiered grading system for dysplasia that utilizes cytological and architectural features, and we require unequivocal evidence of invasion to diagnose adenocarcinoma. In Asia, more emphasis is placed on cytological features in making a carcinoma diagnosis. While this chapter focuses on polypoid gastric dysplasias, the approach to diagnosis and grading is similar for flat dysplasias in the stomach.