Re-Evaluation of Ipsilateral Multiple-Focal Breast Cancer: Case Report and Literature Review.

OBJECTIVE: Ipsilateral multiple breast cancer is a unique situation in which multiple breast cancer lesions are present in the same or different quadrant of the breast. While current research on ipsilateral multiple breast cancer primarily focuses on its existence or heterogeneity, it is important to evaluatethe risk level stratification of heterogenous lesion and determine the intensity of anti-tumor treatments for every lesion, achieving a rational and personalized anti-cancer strategy.

CASE DESCRIPTION: We present a 55-year-old woman with a lump in the lateral quadrant of her left breast, who was diagnosed invasive breast cancer with a background of ductal carcinoma in situ in two lesions of the left breast. The immunohistochemistry examination revealed that the lateral cancer lesion was Luminal B subtype while the lower cancer lesion HER2 positive subtype. Aditionally, the axillary lymph node dissection and immunohistochemistry showed 7 positive lymph nodes originating from ER-positive lesion. After systemic imaging screening, the clinical TNM stage for ER positive subtype was III A and HER2 positive subtype I A. The discovery shifted the conventional understanding that HER2 positive subtype usually had a higher TNM stage than ER positive subtype under the premise of consistent tumor volume and treatment strategy should be readjusted to reduce over-treatment and the risk of recurrence for high-risk tumor. However, little is mentioned about the risk level stratification of foci in ipsilateral multiple breast cancer and its weight in treatment strategy in clinical guidelines for breast cancer.

CONCLUSION: This case highlights the need for more evidence-based data to support risk-level stratification of heterogenous foci and treatment decisions for ipsilateral multiple breast cancer and challenges current clinical practice.