Thyroid-only metastases from other primary cancers are rare and associated with poor prognosis. Breast cancer typically metastasizes to lymph nodes, liver and lungs, while isolated metastases to the thyroid gland are exceptionally rare and often difficult to suspect and differentiate from thyroid cancer (and most frequently poorly differentiated thyroid cancer), even by using fine needle aspiration. A patient with a history of breast cancer (4 years ago) with thyroid-only metastases is presented. Diagnostic and therapeutic problems are discussed and the relevant literature is briefly reviewed. The novelty of this data is that intrathyroid-only metastases from breast cancer are extremely uncommon and indicate generalized disease, and preoperative diagnosis can be difficult, even by using ultrasound-guided fine needle aspiration.