Obstructive nephropathy caused by renal metastasis of papillary thyroid carcinoma: a case report

The aim of this report is to present a rare case of papillary thyroid cancer metastasis to the kidney manifesting with obstructive nephropathy. A 68 year-old man was referred to ultrasound examination because of a multinodular goiter. Ultrasound guided fine needle aspiration biopsy (US-FNAB) suggested follicular adenoma of the right thyroid lobe and a right lobectomy with isthmectomy was performed. Pathohistologic findings confirmed a follicular variant of papillary thyroid carcinoma and the patient underwent a total thyroidectomy followed by radioiodine ablation. A few years later, scintigraphy revealed radioiodine avid metastatic foci in the right kidney as well as an intramuscular lesion in the left thigh. At the same time, non-small cell lung cancer was diagnosed. Papillary thyroid carcinoma is the most common thyroid malignancy, but renal or muscular metastases are extremely rare in this type of cancer and can be found in poorly differentiated cancers, which should be clearly stated in the final pathohistologic report. In order to better the interpretation of these pathohistological findings and allow successful monitoring of these patients, close cooperation with pathologists and immunohistochemical profiling is suggested.