Renal metastases from thyroid papillary carcinoma: Study of sodium iodide symporter expression

Kidney metastases from thyroid cancer are rare. We report two such patients and demonstrate that the in vivo I-131 uptake by the kidney metastasis is associated with high levels of sodium iodide (Na+/I-) symporter (NIS) expre ssion in the first case. Case 1: A 61-year-old woman with papillary thyroid carcinoma-follicular variant (PTC-FV) presented with scapular metastasis. After thyroidectomy and scapulectomy, a I-131 posttherapy scan showed left upper quadrant uptake. A 3.0-cm metastatic PTC-FV deposit was removed by pa rtial nephrectomy. Case 2: A 53-year-old woman presented with back pain. A computed tomography (CT) scan showed a 3.5-cm renal mass, a multinodular go iter, and lung metastases thought secondary to a renal cell carcinoma. A un ilateral nephrectomy revealed metastatic PTC-FV. After thyroidectomy, a I-1 31 posttherapy scan showed lung and skeletal metastases. NIS immunoreactivi ty in tumoral tissue was strongly positive in the primary tumor, shoulder, and kidney metastasis in case 1, as well as in the primary tumor in case 2. Spotty, low-level NIS expression was observed in the kidney metastasis in case 2. In conclusion, kidney metastases of PTC-FV may occasionally retain adequate levels of NIS expression, enabling their detection during life. Th us, intense uptake in the abdomen during I-131 imaging should not be assume d to be physiological gastrointestinal tract residual radionuclide activity .