In the second method by which the predictive values were generated, the calculations were performed using only those specimens that were definitely diagnosed malignant or benign. This was done to determine how reliably the definitive diagnoses were themselves, exclusive of the confounding variable included in the suspicious category. This is to determine how predictive the test was when the pathologist was confident in assigning a definitive diagnosis. When considered by themselves, the malignant and benign diseases posses high positive and negative predictive values, respectively. This indicates that, when a definitive diagnosis is made from FNA, it is a highly accurate and predictive tool.
Interpretative errors are most often responsible for false-positive diagnosis.
In this series, there was a low rate of false- positive results in the group read definitely as malignant. The false-positive specimens were all based on what were adequate specimens. One case was histologically diagnosed as fibroadenoma and the other as benign phyilodies. When the pathologist was confident in diagnosis, it was rarely incorrect. Awareness of these potential pitfalls can be helpful in avoiding a false-negative report in many of these cases.