RESUMEN
OBJECTIVE: Current practice to diagnose pancreatic cancer is accomplished by endoscopic ultrasound guided fine needle aspiration (EUS-FNA) using a cytological approach. This method is time consuming and often fails to provide suitable specimens for modern molecular analyses. Here, we compare the cytological approach with direct formalin fixation of pancreatic EUS-FNA micro-cores and evaluate the potential to perform molecular biomarker analysis on these specimen. METHODS: 130 specimens obtained by EUS-FNA with a 22G needle were processed by the standard cytological approach and compared to a separate cohort of 130 specimens that were immediately formalin fixed to preserve micro-cores of tissue prior to routine histological processing. RESULTS: We found that direct formalin fixation significantly shortened the time required for diagnosis from 3.6 days to 2.9 days (p<0.05) by reducing the average time (140 vs 33 min/case) and number of slides (9.65 vs 4.67 slides/case) for histopathological processing. Specificity and sensitivity yielded comparable results between the two approaches (82.3% vs 77% and 90.9% vs 100%). Importantly, EUS-FNA histology preserved the tumour tissue architecture with neoplastic glands embedded in stroma in 67.89% of diagnostic cases compared to 27.55% with the standard cytological approach (p < 0.001). Furthermore, micro-core samples were suitable for molecular studies including the immunohistochemical detection of intranuclear Hes1 in malignant cells, and the laser-capture microdissection-mediated measurement of Gli-1 mRNA in tumour stromal myofibroblasts. CONCLUSIONS: Direct formalin fixation of pancreatic EUS-FNA micro-cores demonstrates superiority regarding diagnostic delay, costs, and specimen suitability for molecular studies. We advocate this approach for future investigational trials in pancreatic cancer patients.