CASE OF THE MONTH
Pyloric gland adenoma (PGA)
November, 2020
60-year-old female presented with gastric polyp histopathological examination shows Pyloric gland adenoma (PGA) with high grade dysplasia.
Pyloric gland adenoma (PGA) is a rare neoplasm with gastric pyloric gland differentiation that is diagnosed most frequently in the stomach, but also occurs in the duodenum, esophagus, gallbladder, bile duct and rectum. In stomach it accounts for 2.7% of gastric polyps and develop in a background of chronic gastritis with intestinal metaplasia or atrophy, or both. Histologically, pyloric gland adenomas are composed of tightly packed tubules composed of pyloric gland type cells, which are cuboidal or columnar mucus-secreting cells with pale to moderately eosinophilic cytoplasm with absent apical mucin caps. Nuclei are small, round or ovoid, basally located, and often hyperchromatic. Histologically, cells resemble gastric pyloric gland epithelium and Brunner glands. PGA are divided into three categories: those without conventional histological dysplasia, low-grade dysplasia (LGD) and high-grade dysplasia (HGD). Dysplasia is relatively common in pyloric gland adenomas, low- and high-grade dysplasia in 12% and 39% of lesions respectively, and invasive carcinoma in as many as 30%. PGAs with low grade dysplasia show irregularly shaped glands with elongated nuclei and mild cytological atypia. PGAs with High-grade dysplasia are characterized by architectural alterations comprising back-to-back gland and cribriform formation, with nuclear crowding, a greater degree of nuclear enlargement, loss of nuclear polarity, enlarged nucleoli and/or hyperchromasia. PGA tumor cells are positive for MUC6 and negative for MUC2 IHC. Despite the bland histological appearance of most PGAs, a significant number can display features of HGD and may progress to adenocarcinoma.