Needle aspiration cytology of the irradiated breast

During a 3‐year period (1987‐1989), 60 fine‐needle aspiration biopsies (FNAs) were obtained from new breast lesions in patients previously treated by radiation and surgery for breast carcinoma. The lesions occurred at or near the site of previous excision, 3‐117 months after initiation of radiotherapy. FNAs were classified as follows: acellular (11); negative (29); atypical (13); suspicious (4); and positive (3). For statistical analysis, acellular, negative, and atypical diagnoses were considered negative findings, and suspicious and positive diagnoses were considered positive findings. On the basis of subsequent biopsy and/or patient follow‐up, FNA yielded a sensitivity of 86%, a specificity of 98%, a positive predictive value of 86%, a negative predictive value of 98%, and an efficiency of 97%. Excluding cystic lesions, the most reliable criterion for distinguishing malignant from benign lesions was the abundance of epithelial cells, both singly and in large clusters. Cellular characteristics were less helpful, since nuclear atypia was seen in both benign and malignant lesions. It is concluded that (1) FNA is a reliable technique in the evaluation of the irradiated breast; (2) when performed by an experienced operator, an acellular aspirate may be interpreted as evidence against recurrent carcinoma; and (3) epithelial atypia must be interpreted with caution to avoid a false‐positive diagnosis.