Breast cancer to thyroid gland: An unconventional metastatic site

Thyroid gland blood supply is rich but it is not an open area for metastasis. Only 1%-3% of the neoplastic lesions seen in the thyroid are of extrathyroidal origin. Thyroid, lung, bone, lymph node metastasis were detected at the time of diagnosis in a 78-year-old woman with metastatic breast cancer. Control imaging was performed 3 months after hormone therapy was started. All lesions were regressed except thyroid lesion and neck lymph. Tru-cut biopsy was performed to the lesion in the thyroid. The result is consistent with breast cancer metastasis. With this breast cancer metastasis to thyroid case, we want to emphasize the differential diagnosis of neoplastic lesions in the thyroid is important in those diagnosed with malignancy. If there is clinical suspicion after a nondiagnostic thyroid sampling, repeated biopsies should be performed.