Role of sample adequacy in fine needle aspiration biopsy of palpable breast lesions

Background: The role of fine needle aspiration biopsy (FNAB) in breast lesions remains uncertain because its accuracy has been questioned. We hypothesized that this is related to failure to define standards for adequacy of sample preparation. Methods: We reviewed cytology and pathology reports from 351 patients undergoing FNAB at a 350-bed community, university-affiliated teaching hospital over a 2-year period. Patients were included if they had an open biopsy within 2 years of an FNAB of the same lesion. Cytology reports were reviewed by a cytopathologist unaware of the clinical setting or subsequent histology; surgeons unaware of the cytology reports reviewed histology reports. Cytological diagnoses were benign, likely benign, probable cancer, and definite cancer. Samples were characterized as satisfactory, less than optimal (few mammary epithelial clusters), or inadequate (no mammary epithelial clusters.) We assessed the proportion of inadequate samples, the accuracy of FNAB, and the influence of sample adequacy upon FNAB sensitivity. Results: Ninety-nine (28%) FNABs were inadequate, 77 (22%) less than optimal, and 175 (50%) satisfactory. Ninety-five patients (27%) had a final diagnosis of malignancy. FNABs classified as satisfactory or less than optimal and characterized as benign (n = 102) had a negative predictive value (NPV) of 0.91; those termed definite cancer (n = 43) had a positive predictive value (PPV) of 0.98. Only 10% of all cancers were identified in the 28% of FNABs that were classified as inadequate (P <0.01). Conclusions: We concluded that too few FNABs are performed in a fashion that permits definitive cytological interpretation. Inadequate FNABs are less likely to detect malignancy. After excluding inadequate preparations, FNABs interpreted as definite cancer and as benign are highly accurate in identifying patients with and without cancer.