Follicular carcinoma of the thyroid with metastasis to the breast.

A 75-year-old woman with two previous neck operations for follicular carcinoma of the thyroid presented with a breast mass nine years after diagnosis. The mass recurred one month after excisional biopsy. Pathological examination revealed metastatic follicular carcinoma. The breast tumor was weakly positive for estrogen receptor and positive for progesterone receptor. Recurrences in the neck and breast were resected. Residual disease in the neck and metastasis to the lungs were resolved by (131)I ablative therapy. Previous reports of thyroid metastasis to the breast were described as papillary carcinoma. This report describes a rare site of metastasis and briefly reviews the pathology, diagnosis, and management of thyroid carcinoma.