Solitary Metastasis of Clear Renal Cell Carcinoma to Thyroid Gland: Three reported cases with review of the literature.

Metastasis to the head and neck and more specifically to the thyroid gland from distant primary tumors is less common in comparison to the local regional metastasis of squamous cell carcinomas of the upper aero-digestive tract. Preoperative diagnosis of these cases can be difficult. The authors present three cases with distant solitary metastases of clear renal cell carcinoma to the thyroid gland with ambiguous mechanism of tumor spread to the thyroid. Solitary metastases of clear renal cell carcinomas are an uncommon variant of metastasis of this tumor and may imitate thyroid well differentiated carcinoma which most commonly affects the thyroid gland. Therefore, thorough endocrinological investigation of the thyroid gland is necessary. The recommended therapy of renal cell carcinoma metastasis includes surgical removal of all cancerous tissues - i.e. of the gland with the possibly infiltrated adjacent tissues, as well as removal of the affected lymph nodes - selective radical neck dissection. In our study, we discuss the clinical picture, pathology, diagnosis, differential diagnosis and prognosis together with literature review.