Definition of Barrett’s Esophagus
The diagnosis of Barrett’s esophagus requires both endoscopic and histologic evidence of metaplastic columnar epithelium. Endoscopically, there must be columnar epithelium within the esophagus. Histologically, the epithelium must be metaplastic, as defined by the presence of goblet cells. An Alcian blue stain at pH 2.5 stains the acidic mucin present in the goblet cells. The most common errors in the identification of goblet cells are: 1) "pseudogoblet" cells; and 2) Alcian blue positive cells that are not goblet cells.
Pseudogoblet cells are barrel-shaped gastric surface or foveolar cells that do not stain with Alcian blue. These cells commonly have a blush of eosinophilia, due to neutral mucin, on H&E stained sections, in contrast to the blush of basophilia, imparted by the acidic mucin in goblet cells.
Alcian blue positivity in a columnar cell does not necessarily indicate a metaplastic goblet cell; it should have a barrel shape. Other types of cells that can be alcian blue positive but which lack the barrel shape include: reactive gastric foveolar cells, which may be present in the pits and on the mucosal surface, mucous neck cells of the gastric glands, esophageal cardiac glands, and submucosal glands in the esophagus.
As stated above, the diagnosis of Barrett’s esophagus requires both endoscopic and histologic evidence of metaplastic columnar epithelium. The significance of metaplastic columnar epithelium in a biopsy of the GE junction region when the endoscopist has not seen columnar epithelium within the esophagus has not been established.
Pitfalls in the Interpretation of Goblet Cells
Columnar cells which have a barrel shape but which are alcian blue negative should not be interpreted as goblet cells. Often these cells have a pink hue to them as compared to the bluish tinge to goblet cells.
Pseudogoblet cell with pink hue.
Goblet cell with barrel shape and bluish tinge.
Pseudogoblet cells adjacent to true goblet cells.
Alcian blue positive cells which are NOT goblet cells
Alcian blue positivity alone does not define a cell as a goblet cell. We also like to see a barrel shape to the columnar epithelium.
Reactive gastric epithelium showing alcian blue positivity.
Mucous neck cells of gastric glands are typically alcianblue positive.
Submucosal esophageal glands can also show alcian blue positivity.