Objective: To develop a classification scheme for reporting the results of fine needle aspiration (FNA) cytology of a breast lesion according to its likelihood of being a carcinoma.
Study design: To verify the validity of this scheme, we studied a total of 267 FNAs that were prospectively classified according to predefined criteria as positive (76), suspicious (41), proliferative with atypia (66), proliferative without atypia (48) and unremarkable (36), and compared these results with the final histology.
Results: The percentages of patients who had carcinoma on histology were 100% (76), 93% (38), 35% (23), 6% (3) and 31% (11) of cases diagnosed as positive, suspicious, atypical proliferative, proliferative without atypia and unremarkable on cytology, respectively. However, if only invasive carcinoma is considered, then the percentage of carcinoma was 99% (75), 93% (38), 23% (15), 2% (1) and 11% (4), respectively. The only invasive carcinoma in the proliferative-without-atypia category was a tubular carcinoma and represented a false negative diagnosis. All four invasive carcinomas with an unremarkable cytologic diagnosis were due to sampling errors. Definitive surgery after FNA was common in cases with positive (65%) and suspicious (42%) cytologic diagnosis, whereas all but one patient with atypical, proliferative and unremarkable diagnoses had a biopsy initially.
Conclusion: This scheme of reporting breast FNA results with defined criteria according to the probability of identifying carcinoma provides a rational basis for guidelines for the management of breast lesions.