Predictors of malignancy and recommended follow-up in patients with negative endoscopic ultrasound-guided fine-needle aspiration of suspected pancreatic lesions.

Background: Endoscopic ultrasound (EUS) with fine-needle aspiration (FNA) can characterize and diagnose pancreatic lesions as malignant, but cannot definitively rule out the presence of malignancy. Outcome data regarding the length of follow-up in patients with negative or nondiagnostic EUS-FNA of pancreatic lesions are not well-established.

Objective: To determine the long-term outcome and provide follow-up guidance for patients with negative EUS-FNA diagnosis of suspected pancreatic lesions based on imaging predictors.

Methods: A retrospective review of patients undergoing EUS-FNA for suspected pancreatic lesions, but with negative or nondiagnostic FNA results was conducted at a tertiary care referral medical centre. Patient demographics, EUS imaging characteristics and follow-up data were examined.

Results: Seventeen of 55 patients (30.9%) with negative/nondiagnostic FNA were subsequently diagnosed with pancreatic malignancy. The risk of cancer was significantly higher for patients who had associated lymph nodes on EUS (P<0.001) and vascular involvement on EUS (P=0.001). The mean time to diagnosis in the group with falsenegative EUS-FNA diagnosis was 66 days. The true-negative EUSFNA patients were followed for a mean of 403 days after negative EUS-FNA results without the development of malignancy.

Conclusion: For patients undergoing EUS-FNA for a suspected pancreatic lesion, a negative or nondiagnostic FNA does not provide conclusive evidence for the absence of cancer. Patients for whom vascular invasion and lymphadenopathy are detected on EUS are more likely to have a true malignant lesion and should be followed closely. When a patient has been monitored for six months or more with no cancer being diagnosed, there appears to be much less chance that a pancreatic malignancy is present.