CD10 is useful to identify gastrointestinal contamination in endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) cytology from pancreatic ductal adenocarcinoma

ObjectiveEndoscopic ultrasound-guided fine needle aspiration (EUS-FNA) cytology is an effective tool to diagnose pancreatic ductal adenocarcinoma (PDA). Standard morphological criteria are usually reliable. When contaminating gastrointestinal (GI) epithelial cells are prevalent among neoplastic cells, these can be highlighted by carcinoembryonic antigen (CEA) staining. CD10 is a cell-surface metallopeptidase normally expressed by the GI epithelial apical border, whose expression is decreased or lost in PDA. We included CD10 in a panel, together with CEA, to discriminate the GI contaminant cells from PDA cells on cell blocks.MethodsEight cases of EUS-FNA of PDA, featuring both contaminating GI cells and neoplastic cells, whose corresponding cell blocks were available for immunostaining, were selected. CD10 and CEA were stained on cell blocks by standard methods.ResultsCD10 strongly labelled only the GI cells, with a well-defined apical membrane signal; conversely, GI cells did not show CEA staining; benign duodenal cells were faintly labelled in only one case. Malignant cells were positive for CEA and negative for CD10, with the exception of one case with labelled neoplastic cells with weak diffuse cytoplasmic positivity. CD10 apical membrane staining was a feature only seen in benign GI cells.ConclusionsAs a loss of CD10 is a consistent feature of PDA, this marker can be useful, together with CEA, to aid the cytopathologist to identify neoplastic cells in a background rich in GI contaminant cells.