CK19 and CD10 expression in pancreatic neuroendocrine tumors diagnosed by endoscopic ultrasound‐guided fine‐needle aspiration cytology

BACKGROUND: CK19 and CD10 are useful markers in the differential diagnosis of pancreatic tumors. The authors evaluated CK19 and CD10 expression in pancreatic neuroendocrine tumors (NETs) obtained by endoscopic ultrasound (EUS)-guided fine-needle aspiration (FNA). METHODS: Twenty-eight patients diagnosed with pancreatic NETs based on EUS-FNA cytology were studied retrospectively (2004-2007) for immunohistochemical expression of CK19 and CD10. Immunohistochemistry was performed on cell blocks for each case. The pattern of expression for CD10 (cytoplasmic or membranous) and its intensity (0-2) were noted. The staining of the stromal elements for CD10 was recorded as negative. Cytoplasmic staining in tumor cells and percentage distribution (1+ to 4+) for CK19 were regarded as positive. RESULTS: Twenty-three of 28 (82.14%) NETs showed positive cytoplasmic and/or membranous staining for CD10, and 25 of 28 (89.29%) cases were positive for CK19. CONCLUSIONS: The findings demonstrate the high expression of CD10 and CK19 in pancreatic NETs. This indicates that CD10 and CK19 cannot reliably differentiate NETs from other tumors with similar cytomorphologic features (solid pseudopapillary tumors, which frequently stain with CD10, and pancreatic adenocarcinoma, which stains with CK19). Cancer (Cancer Cytopathol) 2009. © 2009 American Cancer Society.