Metachronous Contralateral Breast Cancer Following Treatment of Primary Breast Carcinoma: A Case Report.

Abstract

Bilateral breast cancer is an uncommon clinical entity that may occur either synchronously or metachronously. Metachronous contralateral breast cancer refers to the development of a second primary tumour in the opposite breast after a defined interval following the initial diagnosis. Although relatively rare, it presents important diagnostic and therapeutic challenges and underscores the need for careful long-term surveillance of breast cancer survivors. We report the case of a 42-year-old multiparous woman who initially presented with a long-standing right breast mass with clinical features of locally advanced breast cancer, including peau d'orange, nipple retraction, and ulceration. A core needle biopsy confirmed invasive ductal carcinoma with negative Oestrogen and Progesterone receptors but positive HER2 expression. The patient received neoadjuvant chemotherapy followed by a right modified radical mastectomy and adjuvant chemotherapy. Approximately ten months after the initial diagnosis, she developed a rapidly enlarging mass in the contralateral breast. Histological examination confirmed invasive ductal carcinoma with similar immunohistochemical characteristics. The patient subsequently underwent a left mastectomy and is currently clinically stable under oncological follow-up. Metachronous contralateral breast cancer, although uncommon, remains an important clinical consideration in breast cancer survivors. This case highlights the need for vigilant surveillance of the contralateral breast and timely multidisciplinary management to facilitate early detection and improve patient outcomes.