Breast Cancer Metastases to Atypical Locations: Clinical Insights From Four Cases

Metastatic breast cancer remains the leading cause of cancer-related mortality among women. Common metastatic sites include the lung, liver, bone, lymph nodes, and brain, with distant metastases occurring more frequently than local or regional recurrences. This case series aims to highlight and raise awareness of rare metastatic sites of breast cancer, thereby promoting early detection and guiding optimal management, which may improve patient survival. Four patients were identified with metastases to rare anatomical sites: the parotid gland, thyroid, stomach, and colon. All cases were confirmed by immunohistochemistry, with tumor cells positive for CK7 and GATA-3, consistent with breast origin. ¹⁸F-FDG PET/CT was instrumental in identifying hypermetabolic lesions, though differentiation from primary tumors relied on pathological evaluation. Systemic therapy, including chemotherapy, hormonal therapy, and HER2-targeted treatment, constituted the mainstay of management, with surgical intervention reserved for palliation or local control. Breast cancer metastases to rare sites pose significant diagnostic challenges, often mimicking synchronous primary tumors of the affected organs. Even with advances in oncology care, such metastases may be overlooked unless actively considered. Radiologists and clinicians should maintain a high index of suspicion for atypical metastases in patients with a history of breast cancer. Any new or enlarging lesion in an unusual site should be considered metastatic until proven otherwise. Early detection facilitates timely intervention and may improve patient prognosis.