Specimen adequacy and false-negative diagnosis rate in fine-needle aspirates of palpable breast masses.

BACKGROUND: As fine-needle aspiration (FNA) has become a critical component of the investigation of palpable breast masses, false-negative diagnoses have become a major concern, prompting reevaluation of the definition of specimen adequacy. Although cytopathologists agree that a number of parameters relate to the adequacy of an FNA specimen, there is no unanimity on the role of epithelial cell quantitation in the determination of an adequate FNA. To better understand the significance of epithelial cellularity, false-negative FNA samples from palpable breast lesions were reviewed.
METHODS: False-negative FNA smears of palpable breast masses that had been performed and assessed immediately by cytopathologists were retrieved from the files of The University of Texas M. D. Anderson Cancer Center, and the number of epithelial cell clusters (ECCs) was determined. Aspirates were classified as adequate if a total of six or more ECCs (each comprised of at least five to ten well preserved cells) were present on all slides, or as inadequate if fewer than six ECCs were present.
RESULTS: From 4455 aspirates of palpable breast masses, 51 false-negative aspirates were identified, 41 of which were available for review. No interpretative errors were identified. Twenty-one FNAs (51.2%) were classified as adequate and 20 FNAs (48.8%) as inadequate. The adequate false-negative aspirates contained between 8 to 100 ECCs. A comparison of adequate and inadequate false-negative specimens showed no significant differences in the mean age of patients (56.4 years vs. 57.8 years), the mean number of FNA passes (3.7 passes vs. 3.0 passes), the mean palpation size of the lesions (2.8 cm vs. 2.9 cm), or the mean pathologic size of the lesions (2.1 cm vs. 2.2 cm). Cases of invasive lobular carcinoma were more common in the false-negative smears with fewer than six ECCs.
CONCLUSIONS: Including the number of ECCs as a parameter of adequacy could reduce the rate of false-negative FNA diagnoses of palpable breast masses by approximately 50%. However, the presence or even abundance of ECCs does not eliminate the potential for a false-negative cytologic diagnosis. Cytologic diagnoses must be correlated with clinical and imaging findings (the triple test) to reduce the rate of false-negative cases, but benign triple test results do not entirely exclude the possibility of carcinoma, and such cases require periodic follow-up.