Diagnostic approach to pancreatic tumors with the specimens of endoscopic ultrasound‐guided fine needle aspiration

Endoscopic ultrasound‐guided fine‐needle aspiration (EUS‐FNA) has enabled clinicians to histologically diagnose pancreatic tumors. However, EUS‐FNA specimens often result in tiny fragmented tissues, so auxiliary utilities are necessary. Using immunostaining of CK7, CDX2, neuroendocrine markers and KRAS mutation analysis, we examined 57 FNA cell block sections and 61 surgically‐resected specimens (25 invasive ductal carcinomas, 25 endocrine tumors, and 11 acinar cell tumors). In the majority of the matched pairs, the diagnoses between EUS‐FNA and surgical specimens were concordant using the following criteria: neuroendocrine markers negative, CK7 positive, and mutated KRAS gene for invasive ductal carcinomas; neuroendocrine markers diffusely positive, CK7 and CDX2 negative, and wild‐type KRAS gene for well‐differentiated endocrine tumors; and neuroendocrine markers no more than focal positive, CK7 and CDX2 with various staining patterns, and wild‐type KRAS gene for acinar cell carcinomas. Expression of CK7 and/or CDX2 in addition to KRAS mutations were occasionally seen in endocrine carcinomas, but not in well‐differentiated endocrine tumors, suggesting that ductal differentiation in an endocrine tumor may be a predictor of aggressive disease. The usefulness of these markers was confirmed using 13 additional pancreatic tumors, prospectively. Although minimal in selection, these markers are helpful in making diagnosis from EUS‐FNA specimens of the major pancreatic tumors.