False-negative rate of endoscopic ultrasound-guided fine-needle aspiration for pancreatic solid and cystic lesions with matched surgical resections as the gold standard: one institution's experience.

BACKGROUND: The diagnosis of pancreatic tumors is often complicated because of sampling and interpretive challenges. The current study was performed to determine the rates, types, and causes of diagnostic discrepancies.
METHODS: The authors retrospectively reviewed cytology cases from 2004 to 2010 using matched surgical resection cases as the gold standard.
RESULTS: A total of 733 cases were divided into 3 categories: 1) positive or suspicious (290 cases); 2) negative or atypical (403 cases); and 3) unsatisfactory (40 cases). Of these cases, 101 fine-needle aspiration (FNA) cases had matched surgical resections including 58 positive diagnoses, 39 negative diagnoses, and 4 unsatisfactory diagnoses. All 19 discrepant cases represented false-negative diagnoses without any false-positive cases noted, which included 2 cases with interpretive errors (10%) and 17 cases with sampling errors (90%). All matched cytology cases were divided into 5 subgroups based on the type of lesion or type of error and were analyzed for sensitivity and specificity. The sampling error rate in cystic lesions (8 of 24; 33%) was significantly higher than that in solid lesions (9 of 73; 12%). The false-negative rate in the interpretive error group (3%) was significantly lower than that in the sampling error group (23%).
CONCLUSIONS: The results of the current study confirm that pancreatic endoscopic ultrasound-guided FNA diagnosis has a very low false-positive rate but a relatively high false-negative rate using matched surgical resections as the gold standard. The major cause of a false-negative cytology diagnosis is sampling error and the rate of sampling error in cystic lesions is significantly higher than that in solid lesions.