The Utility of the ThinPrep® for Determining Hormone Receptor and HER2 Status in Axillary Lymph Node Fine-Needle Aspiration in Metastatic Breast Cancer: Comparison with the Primary Tumor.

[INTRODUCTION] Treatment of breast cancer is made on ER, PgR, and HER2 results of primary tumor. However, immunoprofile may differ in axillary metastasis, and treatment may be inadequate or unsuccessful. The objective of this study was to analyze the results of ER, PgR, and HER2 expression and discordance rates in ThinPrep samples from axillary fine-needle aspiration cytology (FNAC) and breast Tru-Cut biopsies.

[METHODS] The study was conducted on 372 cases. Comparative analysis was performed on ER, PgR, and HER2 results of breast Tru-Cut biopsy and axillary FNAC obtained concurrently. A comprehensive review of literature addressing this subject was carried out.

[RESULTS] The results revealed discrepancies between two specimens in 4, 11, and 5 cases for ER, PgR, and HER2, respectively. All discordant cases in ER and PgR and 2 cases in HER2 exhibited a shift from positive to negative. Notably, in 2 cases, HER2 was found to be negative in Tru-Cut biopsy but positive in axillary lymph node FNAC. The HER2 dual silver in situ hybridization amplification was identified in a retrospective analysis of breast Tru-Cut biopsies. The cases examined using the ThinPrep method exhibited 98.93%, 97.1%, and 98.7% concordance for ER, PgR, and HER2, respectively, while the discordance rates were recorded at 1.07%, 2.9%, and 1.3%. The kappa values calculated for ER, PgR, and HER2 were 0.97362 (95% CI 0.94791-0.99932), 0.93443 (95% CI 0.89634-0.97252), and 0.95625 (95% CI 0.91817-0.99432), respectively.

[CONCLUSIONS] The ER, PgR, and HER2 results obtained using the ThinPrep in axillary lymph node FNAC had a lower discordance and higher concordance than the majority of studies in the literature. These results demonstrate that axillary lymph node FNAC and ThinPrep can be safely used for accurate treatment selection and diagnosis.