Cyto-Morphological Correlation of Indeterminate C3 (Atypical) and C4 (Suspicious) Categories in Fine Needle Aspiration Cytology of the Breast

In 1996, to harmonize the reporting system of breast lesions on fine-needle aspiration cytology (FNAC), National Cancer Institute (NCI) proposed five categories from C1-C5. C3 and C4 categories are noted to be ambiguous during histopathological correlation, hence “grey-zoned.” There have been limited researches regarding its usefulness and its histopathological correlation. This study was undertaken to evaluate C3 and C4 categories and to correlate with histopathological examination. This perspective and retrospective study was undertaken for two years. Forty cases of C3 and 32 cases of C4 were retrieved from a total of 602 cases of breast FNAC. Histopathological follow-up and correlation were available in 30 cases of C3 and 15 cases of category C4 and were selected for further study. On the histopathological correlation of the C3 category, 22 (73.3%) cases turned out to be benign, and 8 (26.7%) cases revealed malignant diagnosis, and among the C4 category, 2 (13.3%) cases revealed benign findings, and 13(86.7%) of the cases showed malignancy. This difference was statistically significant (P<0.001). The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of the C4 category in the diagnosis of malignancy were 61.9%, 91.6%, 86.6%, and 73.3%, respectively. FNAC is a simple, rapid, cost-effective, and accurate method to diagnose easily accessible breast swellings. However, one should be aware of its limitations as well. Our study supports maintaining C3 and C4 categories, as there was a statistically significant difference in benign & malignant diagnosis for these categories.