The rate of false-positive results with EUS-guided fine-needle aspiration

The aims of this study were to determine the rate of false-positive diagnosis with EUS-guided fine-needle aspiration and to identify factors contributing to this type of error.

The records of 577 patients undergoing EUS-guided fine-needle aspiration were reviewed and a subset of 188 patients with malignant cytology who underwent surgery was identified. Operative histopathology was compared with EUS-guided fine-needle aspiration cytopathology and false-positive cases were identified. An experienced cytopathologist, who was not involved with the original interpretation of the specimens, reviewed these cases to identify any factor(s) contributing to the errors.

Three cases of false-positive diagnosis were identified (1.6%; 95% CI [0.3%, 4.6%]). By aspiration site, the false-positive rates were as follows: pancreas 2/39 (5.1%), 95% CI [0.6%, 17.3%]; lymph nodes 1/136 (0.7%), 95% CI [0.02%, 4.0%]; and other sites 0/13, 95% CI [0.0%, 24.7%]. In both instances of a false-positive diagnosis for a pancreatic aspiration cytologic specimen, interpretative errors were identified. The false-positive interpretation of cytologic material aspirated from a lymph node occurred in a patient without any evidence for malignancy at surgery. In 111 patients with confirmed esophageal, gastric, or rectal malignancy undergoing EUS-guided fine-needle aspiration of nonperitumoral lymph nodes, there was no false-positive diagnosis, suggesting that specimen contamination by luminal tumor is rare.

The overall rate of false-positive diagnosis for EUS-guided fine-needle aspiration is similar to that reported for other modalities. Most false-positive diagnoses are caused by interpretation errors.