Expression of p63 immunostaining in liquid-based cytology (BD SurePath) of breast fine-needle aspiration

Background Methods We performed p63 immunostaining to detect myoepithelial cells on BD SurePath liquid-based cytology (LBC) slides and examined whether this improved the diagnostic accuracy in breast fine-needle aspiration cytology (FNAC). We examined the diagnostic accuracy using the LBC-p63 immunostaining slides of 298 lesions obtained from July 2010 to August 2016. Results Conclusion We defined the cutoff values for malignancy as follows: (1) the percentage of p63+ cluster was <30%, (2) the percentage of p63+ single cells in cell clusters was <3%, (3) the number of p63+ single cells in the background was <20 when the total number of the cell clusters was <100, or the number was <120 when the total number was >= 100. The malignant lesions showed significantly lower values than the benign lesions in the percentage of p63+ clusters, the percentage of p63+ single cells in the clusters, and the number of p63+ single cells in the background (P < .001). The diagnostic values obtained only by Papanicolaou staining vs the improved values with LBC-p63 immunostaining slides were as follows. Sensitivity, 88.3% to 99.0%; specificity, 89.1% to 99.0%; positive predictive value, 94.8% to 99.5%; negative predictive value, 77.4% to 97.8%; diagnostic accuracy, 88.6% to 99.0%, respectively. The diagnostic accuracy of breast FNAC was significantly improved by adding LBC-p63 immunostaining.