Primary Small Cell Carcinoma of the Breast: When a Rare Tumour is Real

Abstract

Background: Extra-pulmonary small-cell neoplasms are rare, and treatment planning is challenging for clinicians. The lack of guideline-based management undermines and isolates patients for whom these cancers are not just rare but also real. Small-cell breast cancer (SCBC) is a rare, aggressive disease that accounts for less than 1% of all invasive breast cancers. Here, we report a case of SCBC and discuss the complexities of case management. Case Presentation: A 46-year-old patient presented with a self-detected right breast lump. Mammogram and ultrasound examination showed a 69x47mm dense lesion in the upper outer aspect of the right breast and a 17mm pathologic node in the inferior right axilla. The triple assessment demonstrated a localised high-grade malignant neuroendocrine neoplasm. Management extrapolated from small cell lung cancer management and case reports, consisted of chemotherapy with carboplatin, and etoposide introduced with concurrent radiotherapy, followed by mastectomy with axillary lymph node dissection. A complete pathological response was obtained. Six months following her surgery, metastatic disease in the brain, chest wall, lymph nodes, and lungs developed. Rechallenge with carboplatin and etoposide led to a brief response, and subsequent immunotherapy was ineffective. Conclusion: This case report highlights the challenges of rare tumour management. Establishing registries for these and other rare tumors would facilitate care, reduce patient uncertainty and assist in founding protocol-based care.