We report a case of bilateral breast cancer associated with Graves' disease characterized by a large goiter and complicated by a severe ophthalmopathy. The hyperthyroidism was treated initially with methimazole and then with thyroidectomy, the ophthalmopathy with intravenous steroids combined with orbital radiotherapy. The breast tumors underwent surgical resection followed by chemotherapy. We describe this case because of the well-known association between breast cancer and thyroid disease, particularly of the autoimmune type, the causes of this being still unclear. Recent literature on this topic is reviewed, discussing the possible role of the Na(+)-I(-) symporter and anti-TPO antibodies.