Predictive power of cytomorphological features in equivocal (C3, C4) breast FNAC

Definitive immediate diagnosis in breast fine needle aspiration cytology (FNAC) remains the aim for cytopathologists. We reviewed 72 consecutive equivocal (C3 and C4) aspirates with respect to 16 cytomorphological criteria. We assessed the power of each criterion at predicting either a malignant [positive predictive value (PPV)] or a benign [negative predictive value (NPV)] diagnosis by correlation with follow-up histology. Blind review led to 34% of cases being correctly definitively diagnosed. Eccentrically placed epithelial cell nuclei (PPV = 88%, sensitivity = 67%, specificity = 87%) and coarse nuclear chromatin (PPV = 81%, sensitivity = 72%, specificity = 83%) are the features that are most useful in predicting malignancy in this selected series. The presence of myoepithelial cells within epithelial groups is not a good indicator of a benign diagnosis (NPV = 24%, sensitivity = 80%, specificity = 53%).