Cytomorphology and B72.3 labeling of benign and malignant ductal epithelium in pancreatic lesions compared to gastrointestinal epithelium

Endoscopic ultrasound-guided pancreatic fine-needle aspiration biopsy very frequently produces gastrointestinal epithelial contamination (GIC). We studied the cytomorphology and B72.3 immunoreactivity of lesional epithelium of benign and malignant ductal lesions of the pancreas and compared the findings to our previously established template of GIC. Air-dried smears, fixed smears, and ThinPrep® (TP) specimens were obtained using a cytobrush, directly from benign and malignant ductal lesions of 18 Whipple specimens, to ensure purity of the epithelium studied. Smear background, cell architecture, and cellular features were analyzed. Immunocytochemical staining with B72.3 was performed in 14 cases. Epithelium of ductal carcinoma was distinguished from benign ductal epithelium in chronic pancreatitis and GIC primarily by crowded architecture and atypical cellular features, including high nuclear-to-cytoplasmic ratio, irregular nuclei, nucleoli, and vacuolated cytoplasm. Benign ductal and GIC epithelium were only distinguished by architecture (goblet cells and brush borders), but not consistently, especially gastric epithelium that lacked these features. B72.3 shows promise in the differentiation between GIC and benign and malignant ductal epithelium, with no staining supporting benign ductal cells, fine punctate perinuclear staining correlating with GIC, and strong cytoplasmic staining supporting malignancy.