Cytomorphology of gastric and duodenal epithelium and reactivity to B72.3: a baseline for comparison to pancreatic lesions aspirated by EUS-FNAB

Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNAB) has become a widely used method of pre-operatively evaluating pancreatic masses. This technique introduces gastrointestinal contamination into the specimen, which poses a diagnostic pitfall. The cytomorphologic features of these contaminants have not been fully characterized. The current study was designed to systematically document the cytomorphology of gastric and duodenal epithelium on fixed and air-dried smears, as well as ThinPrep (TP) preparations, and to assess the reactivity of the epithelial cells to the tumor marker B72.3 so as to establish a baseline for future comparative studies with EUS-FNAB of the pancreas. Air-dried and fixed smears and TP specimens were obtained using a cytobrush from gastric (GM) and duodenal (DM) mucosa from 14 Whipple specimens. Cytologic features of cell architecture, cellular features and smear background were analysed. Immunocytochemical staining with B72.3 was performed in 10/14 cases. Mucin was present in all preparations except one case from the duodenum. It was consistently present as isolated thick to thin clumps but never as diffuse 'colloid-type' mucin; it was most prominent on air-dried smears, and most abundant from the GM. Epithelial cells were admixed with mucin, but degenerated cells and inflammation were not present within the mucin. Mucin on TP appeared as fragmented wisps of pale blue staining material. Background inflammation and debris were not significant findings. The epithelial cells were arranged in large and small monolayered sheets. Smaller groups were more common from GM on smears and more abundant on TP than smears. Luminal edges (DM>GM) were a prominent feature, with a brush border noted in DM. The nuclei of GM and DM were round, evenly spaced and without atypia, and dense, non-vacuolated cytoplasm was the rule, with the exception of goblet cells and occasional gastric foveolar cells noted in one case. In both GM and DM, B72.3 stained goblet cells with a strong, coarsely granular pattern and stained epithelial cells focally in a finely granular, punctate, perinuclear distribution; mucin also stained strongly in all cases. These baseline characteristics provide a template for assessing mucin and epithelial GM and DM contamination on pancreatic EUS-FNAB specimens.