Endoscopic Ultrasound (EUS)-guided Fine Needle Biopsy (FNB) in the histological evaluation of patients with chronic pancreatitis

Background: Histological diagnosis of chronic pancreatitis has been classically limited to the study of surgical specimens. Since pancreatic biopsies are rarely done in the context of chronic pancreatitis, histological characteristics at different stages of the disease are unknown. Aim: To evaluate the histological characteristics of chronic pancreatitis in samples obtained by pancreatic EUS-FNB, and the relationship with EUS findings. Methods: Fourteen consecutive patients (14 male, mean age 66 years, range 17–81 years) with known chronic pancreatitis, who underwent EUS-FNB for the study of pancreatic masses were included. EUS-FNB was performed under conscious sedation with a 22G needle guided by the lineal scanning Pentax FG-38UX echoendoscope. EUS criteria for the diagnosis of chronic pancreatitis were evaluated: parenchymal criteria included hyperechoic foci, hyperechoic strands, lobularity, cysts and calcifications; and ductal criteria included dilation, duct irregularity, hyperechoic duct margins, visible side-branches and intraductal calcifications. Following histological features were evaluated: presence of acini, ductal epithelium, fibrotic tissue (collagen) and inflammatory infiltration. Results: Adequate tissue sample for histological evaluation was obtained in all cases. Infiltration by inflammatory cells was observed in all tissue specimens. Samples included pancreatic acini in five cases (35.7%), in number of 2 to 13 acini each. In the remaining 9 cases (64.3%) the presence of ductal epithelium together with fibrotic tissue was observed. Biopsies including pancreatic acini were those obtained from patients with mild to moderate EUS changes of chronic pancreatitis (up to 5 EUS criteria). On the contrary, biopsy samples from more severe cases (8–10 EUS criteria) were those showing only ductal ephitelium with fibrotic component. Conclusion: EUS-guided pancreatic biopsy allows evaluating histological changes of all stages of chronic pancreatitis. This may be an important advance for a better knowledge of the disease.