Assessment of HER2 Expression in Primary Lesions and their Metastatic Lymph Nodes in Breast Cancer Patients With Positive Axillary Lymph Nodes

摘要

Human epidermal growth factor receptor type 2 (HER2) is a target protein of the gene-targeting drug trastuzumab. Since the prescription of trastuzumab is determined by the HER2 expression in primary tumors, it is essential to corroborate the HER2 expression in primary tumors and their metastatic lesions. Therefore, we compared the HER2 expression in the primary tumors of 107 postoperative cases with that in all 787 corresponding metastatic lymph nodes. In 74 of 107 cases (69.2%) HER2 scores between primary tumors and metastatic lymph nodes coincided however did not in 33 (30.8%). Maximal HER2 scores of metastatic lesions were lower than those in primary tumors in 13 of 33 cases. Conversely, metastatic lesions showed higher maximal scores than did primary tumors in 11 cases. Moreover, in 16 cases, HER2 scores were not uniform between different metastatic lesions in the same patient Primary tumors in 41 of 107 cases (38.3%) were found by heterogeneous staining. In 74 cases, in which HER2 scores were concordant between primary tumors and metastatic lesions, the primary tumors were not uniformly stained in 17 (23.0%). Of the remaining 33 cases, primary tumors were not uniformly stained in 24 (72.7%). Staining variability in metastatic lesions could have contributed to this heterogeneity of primary tumors. And this heterogeneity is one of the reasons for resistance to trastuzumab therapy.