Metaplastic breast carcinoma: a rare and aggressive entity.

Introduction: Breast cancer (BC) remains the most prevalent malignancy among women globally, encompassing a variety of tumor subtypes with differing biological behaviors, prognoses, and responses to treatment. Among these, invasive ductal carcinoma (IDC) is the most common, followed by other subtypes such as lobular carcinoma and triple-negative breast cancer. Metaplastic breast carcinoma (MpBC) is a rare and highly aggressive form of BC, representing less than 2% of cases. Characterized by its heterogeneous nature and poorer prognosis compared to other BC subtypes, MpBC often presents significant diagnostic and therapeutic challenges. Case description: We present the case of a 70-year-old woman who presented to our breast care clinic with right mastodynia following a recent trauma. She reported a palpable retro-areolar mass in the right breast that had increased in size over several years and was associated with calcifications. Imaging studies, including mammography and ultrasound, revealed a 3-cm irregular, heavily calcified mass with indistinct borders. Histological analysis of a biopsy confirmed metaplastic carcinoma with chondrosarcoma and osteosarcoma elements, high histological grade, and lymphovascular involvement. The patient underwent successful tumor excision with sentinel lymph node removal. Adjuvant chemotherapy and radiotherapy were planned based on a multidisciplinary team's recommendations. Discussion: MpBC typically presents as a palpable, irregular mass that may exhibit rapid growth or changes, often complicating its differentiation from other breast malignancies. Standard imaging techniques like mammography and ultrasound may fail to clearly distinguish MpBC from other tumors, leading to potential misdiagnosis. The heterogeneous nature of MpBC, with both epithelial and mesenchymal components, poses additional challenges in diagnosis and treatment. Although MpBC is generally more aggressive and less responsive to conventional therapies compared to IDC, recent analyses suggest that, when adjusted for confounding factors, survival outcomes for MpBC may align more closely with those of aggressive IDC subtypes. Current treatment strategies include surgery, chemotherapy, and radiotherapy, with emerging targeted therapies offering potential for improved outcomes. Conclusion: MpBC remains a rare and challenging BC subtype with a typically poor prognosis. Our case highlights the diagnostic difficulties and the aggressive nature of MpBC. Despite its severe clinical features and histological grades, survival outcomes for MpBC may be comparable to those of aggressive IDC subtypes when appropriate treatment adjustments are made. Continued research into targeted therapies and novel treatment approaches is essential to enhance management strategies and improve outcomes for patients with MpBC.