THE RELIABILITY OF ENDOSCOPIC ULTRASOUND (EUS)-GUIDED FINE NEEDLE ASPIRATION (FNA) FOR DIAGNOSING SOLID PANCREATIC LESIONS

Abstract

Purpose: The development of EUS-FNA has revolutionalized our ability to differentiate benign from malignant pancreatic masses. The purpose of this study was to assess the diagnostic accuracy of EUS-FNA in patients with solid pancreatic lesions. Methods: All patients referred for EUS evaluation of solid pancreatic mass between 1998 and 2002 were reviewed. Patient demographics and clinical history were recorded. Cytopathology was compared with operative histopathology in patients who underwent surgery. Patients who did not have surgery were followed clinically. Results: A total of 302 patients (mean age 69, 172 M/130 F) underwent EUS-FNA for solid pancreatic lesions. FNA was consistent with pancreatic malignancy in 53% (160/302) while 39% (117/302) had no evidence of malignancy. In the remaining 8% (25/302), biopsy was inconclusive. Of the pancreatic cancer patients, 90% (144/160) had adenocarcinoma, 4% (6/160) had neuroendocrine tumors, and 6% (10/160) had other malignancies. In the group with a definitive FNA diagnosis, 27% (74/277) underwent surgery and operative histopathology was compared with FNA cytopathology. There were one false positive and four false-negative FNA diagnoses; and the sensitivity, specificity, PPV, and NPV were 92%, 97%, 98% and 89% respectively. The false-positive diagnosis was due to misinterpretation by the initial pathologist. In the 4 false-negative cases, 75% (3/4) had cytologic evidence of chronic pancreatitis. In patients with an inconclusive FNA, 32% (8/25) had surgery and 5 had adenocarcinoma. The remaining 70% (220/302) of patients who did not undergo surgery were followed clinically. The mean survival for patients with a positive, negative, and inconclusive FNA was 18, 48, and 31 months respectively. Conclusions: 1. EUS-FNA accurately provides a cytologic diagnosis in most patients with solid pancreatic lesions. 2. Cytologic evaluation of pancreatic tissue in the setting of chronic inflammatin can be difficult. 3. A false-positive diagnosis was uncommon and in this study was due to interpretation error. 4. A proportion of patients with inconclusive EUS-FNA may have underlying cancer and should be followed carefully.