The accuracy of malignant diagnoses established by fine needle aspiration cytologic procedures of mammary masses.

Fine needle aspiration cytologic studies are being used with increasing frequency to diagnose carcinoma of the breast. To determine whether or not a diagnosis of carcinoma established by cytologic examination is sufficiently accurate to proceed to treatment without tissue confirmation, we have examined our results in a series of 109 patients who had 111 aspiration cytologic procedures followed by open biopsy between January 1985 and June 1987. From this group, 39 specimens were read as malignant and 19 were read as suspicious. Thirty-eight of 39 specimens with positive readings were from lesions that proved to be malignant on subsequent open biopsy. Seventeen of 19 suspicious specimens were also from malignant lesions. Three of 17 specimens that were inadequate and nine of 36 negative specimens were from lesions that were later shown to be malignant. Our single false-positive result occurred on cells that had been air dried during preparation in the early months of experience with this technique at our institution. Re-evaluated later in our series, the same specimen was called suspicious rather than malignant. We conclude that a positive reading on fine needle aspiration is highly accurate. The positive predictive value should be 100 per cent, once experience is gained in preparing and interpreting the material. Open biopsy is necessary for inadequate, negative or suspicious specimens to exclude a malignant lesion if the clinical or mammographic findings are consistent with carcinoma.