Renal metastasis from papillary thyroid microcarcinoma.

Papillary or follicular microcarcinoma of the thyroid comprises 10-20% of all thyroid malignancies. Most of these diseases exhibit slow progression and have a favorable prognosis. Distant metastasis caused by thyroid microcarcinoma is uncommon, and is usually found in the lung or bone. Thyroid microcarcinoma with metastasis to the kidney has not previously been reported. Clinically detectable well-differentiated metastatic thyroid carcinoma to the kidney is rare, and only 16 cases have been reported. Herein we describe a case of metastatic papillary thyroid microcarcinoma to the kidney in a patient with a pelvic fracture and pulmonary metastasis. The patient underwent a total thyroidectomy, radiotherapy, ablation treatment with 131I and thyroxine suppressive therapy. In conclusion, microcarcinoma cannot be ignored. Although uncommon, metastases may arise.