Evaluation of HER۲ Positivity Based on Clinicopathological Findings in HER۲ Borderline Tumors in Iranian Patients with Breast Cancer

Background & Objective: Human epidermal growth receptor-۲ (HER۲) gene amplification is an important predictive and prognostic factor in breast cancer treatment. However, the expression of HER۲ determined by immunohistochemistry (IHC) is considered as borderline in some cases, and confirmation of the HER۲ status by either fluorescent in situ hybridization (FISH) or chromogenic in situ hybridization (CISH) is necessary for correct treatment decision-making. Considering the high cost of FISH and CISH, we aimed to investigate whether clinicopathological findings of the tumor could predict the HER۲ status.  Methods: A retrospective study was performed using the data from ۵۸۴ patients with breast cancer with HER۲-borderline disease, confirmed by IHC. Final HER۲ status, pathologic tumor size and type, nodal involvement, Ki۶۷ index, presence of estrogen and progesterone receptors (ER, PR), lymphovascular invasion (LVI), and stage were retrieved from the clinical records.Results: One hundred twenty-one (۲۰.۷%) patients were HER۲-positive according to the FISH or CISH results. Logistic regression analysis showed that the pathologic size was positively associated with HER۲ positivity with an odds ratio (OR) of ۱.۰۲ (۹۵% CI: ۱.۰۱-۱.۰۴). In addition, the adjusted OR illustrated a statistically significant association between HER۲ positivity and PR negativity (OR= ۲.۲۲, ۹۵% CI: ۱.۲۹-۳.۸۳).Conclusion: In HER۲ borderline breast cancer, HER۲ positivity significantly increases with tumor size and PR negativity. Further studies are recommended that may find an applicable model to predict the actual status of HER۲ in borderline cases.

Keywords:

Breast cancer , Her۲ , Hybridization in Situ