[Pathological diagnosis of solid pancreatic lesions with endoscopic ultrasound-guided fine needle aspiration: a series study of 311 cases].

Objective: To investigate the combined application of cytology, cell block histology and immunohistochemistry to improve the diagnostic accuracy of solid pancreatic lesions in endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) samples. Methods: The pathological data of EUS-FNA in 311 cases of solid pancreatic lesions submitted to the Second Hospital of Hebei Medical University, Shijiazhuang, China from May 2019 to September 2023 were retrospectively analyzed. The cases included pancreatic ductal adenocarcinoma (PDAC, 172 cases), solid pseudopapillary neoplasm (SPN, 12 cases), neuroendocrine tumors (PNET, 14 cases) and chronic pancreatitis (113 cases). The cytological features of smears, the histology of cell block sections and the diagnostic markers in PDAC, SPN and PNET were analyzed. The diagnostic accuracies of cytology, cell block histology/immunohistochemistry and combination of the two methods for classifying these pancreatic solid lesions were evaluated. Results: Irregular arrangement of atypical (cancer) cells, anisonucleosis and nuclear atypia were the typical cytological features of PDAC, while presence of pseudopapillae with a myxoid/hyalinized fibrovascular core and low adhesion/salt-and-pepper chromatin were diagnostic features of SPN and NET, respectively. Immunohistochemical results showed that CK7 and CK19 were the most sensitive markers of pancreatic ductal epithelia, and the diffuse strong expression of S-100P (102/111, 91.9%) and aberrant expression of p53 (80/111, 72.1%) were important immunophenotypic markers of PDAC. Various degrees of CDX2 expression could be found in 66.4% PDAC. The expression of CD10, PR, vimentin, CD99 and cyclinD1 and the aberrant expression of β-catenin were the immunophenotypic features of SPN, while the expression of CgA, Syn and CD56 were indispensable immunemarkers for the diagnosis of PNET. Overall, cytology had higher sensitivity than cell block histology (93.9% versus 82.8%) and lower specificity (92.9% versus 99.1%), while the combination of the two methods significantly improved the sensitivity to 96.9% in solid pancreatic lesions. The combination of cytology and cell block histology could significantly improve the diagnostic efficacy of EUS-FNA in PDAC. Conclusions: Integrated diagnosis based on cytology (including rapid on-site evaluation), cell block histology and immunohistochemical findings could significantly improve the diagnostic yield of EUS-FNA in classifying solid pancreatic lesions.