Correlations between HER2 Expression and Other Prognostic Factors in Breast Cancer: Inverse Relations with the Ki-67 Index and P53 Status.

BACKGROUND Overexpression or amplification of human epidermal growth factor receptor-2 (HER2) is associated with grade of malignancy and a poor prognosis in breast cancer (BC). The aim of this study was to evaluate of value of HER2 as a prognostic marker, and to analyze associations with common histopathological parameters in BC cases. MATERIALS AND METHODS Between of 2007 to 2014, 260 patients with BC referred to Oncology Clinic provided cancer tissue samples which underwent immunohistochemistry (IHC) for markers. ER and PR positivity was defined as ≥10% positive tumor cells with nuclear staining. HER2-positive was defined as either HER2 gene amplification by fluorescent in situ hybridization (FISH) or scored as 3+ by IHC. For HER2 (2+), FISH was performed to determine HER2 positivity. RESULTS The mean age at diagnosis for the patients with HER2-negative was significantly higher than in HER2-positive cases. Also, there were significant correlations between histological grade, nuclear grade, lymph node metastasis, tumor size, ER status, PR status, p53 overexpression and Ki-67 index with HER2 expression. HER2-negative lesions were of higher grade and more likely to be ER-negative, PR-negative, p53-positive, lymph node metastasis, with a tumor size<2cm and also Ki-67≥20% as compared to the HER2-positive group. CONCLUSIONS Contrary to the results of other studies, HER2-positive tumors in our study had a lower Ki-67 index and were p53-positive. Also, Ki-67 proliferation index ≥20% in more studies was associated with p53-positive.Therefore, tumors which are HER2-positive and have a Ki-67≥20% had a more aggressive behavior compared to HER2-positive and Ki-67<20% lesions.