Breast fine-needle aspiration. A comparison of ThinPrep and conventional smears.

Fine-needle aspiration (FNA) of the breast has been used in our institution since 1969. In August 1993, ThinPrep (Cytyc Corp, Boxbotough, MA) processing of breast FNA biopsy specimens was introduced. Comparing conventionally prepared breast FNA specimens (21,193 cases) with ThinPrep processed material (7,903 cases) shows a decrease in the unsatisfactory rate with the ThinPrep processing (29.5% to 27.7%) with no significant change in sensitivity (84.4% vs 86.3%) or positive predictive value (96.5 vs 95.0%). However, there is a slight decrease in specificity (98.6% vs 96.5%) and negative predictive value (91.1% vs 88.0%) with the ThinPrep specimens. The results span 28 years, during which time the breast cancer population has changed, with a higher prevalence of malignancy in the last decade of our study. When the 4 most recent years of conventional cytology are compared with the 4 years of ThinPrep processing, there is no significant difference in diagnostic accuracy. The results of the present study show that the ThinPrep processing technique provides an effective method for preparing breast FNA. specimens.