Most doctors consider FNA to be a very good test. Overall, it is about 90-95% accurate when the aspiration and interpretation are done by an experienced cytopathologist. There is a small chance (usually less than 10%, depending on the size, location and nature of the lump) that the FNA will not be interpreted as cancer when cancer is there. Very rarely (usually less than 1% of the cases), FNA may be falsely interpreted as cancer when cancer is not there. Your doctor will use the results of the FNA and other clinical information to determine if further tests or treatment are necessary.