Immunocytochemical evaluation of estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 in breast cancer cell blocks and corresponding tissue blocks: A single institutional experience

Background: Immunohistochemistry (IHC) is a routinely performed method to demonstrate estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) in surgical breast cancer specimens but not on cell block (CB) of fine-needle aspiration (FNA). The aims of this study were to evaluate the expression of ER, PR, and HER2 using immunocytochemistry (ICC) on CB and compare with the corresponding tissue blocks as gold standard as well as to compare with other similar studies. Materials and Methods: Forty-eight breast carcinoma CB specimens with their corresponding tissue blocks were identified. ICC on CB for ER, PR, and HER2 was performed and compared with tissue blocks. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value were measured for each receptor. The degree of agreement between CB and tissue blocks was calculated using Cohen's kappa (κ) test. Results: ER results showed 67.7% sensitivity, 94.1% specificity, 95.5% PPV, and a moderate agreement (κ =0.588). PR results showed 50% sensitivity, 90% specificity, 87.5% PPV, and a fair agreement (κ =0.368). HER2 results showed 58.3% sensitivity, 100% specificity, 100% PPV, and a moderate agreement (κ =0.539). Conclusion: The results of this study confirm the wide variations that occur between CB ICC and tissue block IHC in the detection of ER, PR, and HER2 in breast cancers. In comparison with other studies, we report a low sensitivity and high specificity rates for ER, PR, and HER2 in FNA CB. Further studies are recommended.