Metachronous Bilateral Breast Carcinoma: A Diagnostic Challenge in Distinguishing Second Primary from Metastatic Disease
Authors: Dr Purnopama Puja, Dr Nishat Tasnim
Institution: Rajshahi Medical College, 250bedded Mohammad Ali Hospital, Bogura
Introduction
Metachronous bilateral breast carcinoma is an uncommon clinical entity characterized by the development of a second primary malignancy in the contralateral breast after a disease-free interval. The appearance of a new contralateral breast lesion in a previously treated patient poses an important diagnostic challenge in distinguishing a second primary malignancy from metastatic recurrence. We report the case of a 60-year-old woman with hormone receptor-positive, HER2-negative invasive ductal carcinoma of the left breast who underwent neoadjuvant chemotherapy followed by modified radical mastectomy and subsequently received adjuvant endocrine therapy with letrozole. Approximately three years later, she presented with left chest-wall swelling, ipsilateral upper-limb lymphoedema, and multiple right breast lumps, raising suspicion of recurrent or metastatic disease. However, histopathological and immunohistochemical evaluation of the contralateral breast lesion supported a metachronous second primary breast carcinoma rather than metastatic involvement. This case highlights the occurrence of a second primary breast malignancy despite prior systemic treatment and ongoing endocrine therapy, emphasizing the importance of accurate pathological differentiation because of its distinct prognostic and therapeutic implications. Keywords: Metachronous bilateral breast carcinoma, contralateral breast cancer, second primary malignancy, invasive ductal carcinom
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