Background: Many studies have confirmed that a diagnosis of malignancy by cytology is highly reliable, and very few false-positive diagnoses have been recorded. However, the technique is limited by modest diagnostic sensitivity, so that a negative cytologic report is of less value. Human telomerase reverse transcriptase (hTERT), one of the subunits of telomerase, is a promising diagnostic marker for pancreatic cancer.Objectives: To evaluate the feasibility of detection of hTERT expression by immunohistochemistry (IHC) for preoperative diagnosis of pancreatic malignancy.Methods: hTERT expression was examined by IHC in preoperative pancreatic juice samples.Results: In pancreatic juice samples, hTERT expression was detectable in 84% of pancreatic ductal adenocarcinomas (PDACs), while 62% of PDACs were positive by cytology. In intraductal papillary mucinous neoplasms (IPMNs), hTERT expression was detectable in 88% of malignant IPMNs, while only 22% were positive by cytology. The sensitivity, specificity, and overall accuracy of hTERT expression for differentiation between carcinoma and other benign diseases were 85.1%, 82.1%, and 84.3%, respectively, where as the same values for cytologic accuracy were 47.1%, 89.3%, and 57.4%, respectively. When the results of cytology and hTERT expression were combined, the sensitivity and overall accuracy increased to 92.0% and 87.8%, respectively.Conclusions: Our results suggested that the assessment of hTERT expression in preoperative pancreatic juice increased the sensitivity and accuracy of diagnosis of PDACs and malignant IPMNs.