Ultrasound-guided fine-needle aspiration (FNA) of nonpalpable breast lesions - A review of 1885 FNA cases using the National Cancer Institute-supported recommendations on the uniform approach to breast FNA

BACKGROUND. A probabilistic approach to the classification of fine-needle a spirates (FNAs) of the breast recently was recommended and received endorse ment from the National Cancer Institute (NCI). In this system, FNAs are cla ssified as benign, indeterminate/atypical, suspicious/probably malignant, a nd malignant, but to the authors' knowledge the use of these diagnostic cat egories has not been evaluated on a large scale. Furthermore, this classifi cation scheme has nor been applied to FNAs of nonpalpable lesions of the br east obtained under imaging guidance. Thus, the current study focused on wh ether the diagnostic categories could be applied usefully to ultrasound-gui ded FNAs (US-FNAs) of nonpalpable breast lesions. METHODS. Between 1988-1996, 1885 US-FNAs were performed on 1639 patients. T he original FNA diagnoses were reclassified into the NCI-supported recommen dations for diagnostic categories of breast FNAs. The cytologic findings we re correlated with the tissue specimens, which were available in 851 cases, or with clinical follow-up of a minimum of 2 years in 127 of the 274 patie nts with benign solid lesions. RESULTS. The 1885 cases were categorized as follows: 1057 (56.1%) as benign , 86 (4.6%) as atypical, 79 (4.2%) as probably malignant, 502 (26.6%) as ma lignant, and 161 (8.5%) as unsatisfactory (defined as < 6 epithelial cell g roups on all slides). The benign US-FNAs included 480 (45.4%) cysts and 577 (54.6%) solid lesions. Combined clinical and surgical follow-up showed tha t the frequency of malignancy was 3.7% in US-FNAs classified as benign, 52. 9% in those designated as atypical, 75.8% in those designated as suspicious , and 98.9% in those classified as malignant. Based on combined histologic and clinical follow-up, a sensitivity of 97.1% and specificity of 99.1% wer e found for US-FNAs when definitive benign and malignant diagnoses were con sidered. A false-negative rate of 3.7% was attributed to sampling error. A false-positive rate of 0.68% was secondary to interpretative error of proli ferative lesions. CONCLUSIONS. Application of the NCI-supported diagnostic categories to US-F NA of nonpalpable breast lesions is useful in stratifying aspirates based o n the likelihood of underlying malignancy. The subcategories of US-FNAs dia gnosed as atypical have similar probabilities of malignancy; this justifies their being grouped as a single category wherein tissue biopsy would be re quired to exclude carcinoma. Benign and inadequate FNA diagnoses must be co rrelated with the clinical and imaging findings and in noncorrelative cases the patient should undergo biopsy. US-FNA is a sensitive and specific mean s with which to diagnose nonpalpable breast lesions. [See editorial on page s 1-4, this issue.] Cancer(Cancer Cytopathol) 1999;87:19-24. (C) 1999 Ameri can Cancer Society.