Management of thyroid nodules as secondary involvement of renal cell carcinoma: case report and literature review.

Literature reports intra-thyroid involvement of renal cell carcinoma (RCC) as a very rare and late event after kidney cancer diagnosis. Nevertheless, it must be investigated and differentiated from primary thyroid nodules. This is important in order to give the patient the best and earliest treatment. In fact the presence of thyroid metastasis of RCC is often the expression of a systemic disease and therefore the patient should have a complete total body examination in order to rule out any other organ involvement. In the case of a solitary metastasis, the therapeutic approach is thyroidectomy giving the patient a survival benefit. Here, a case report of a solitary RCC thyroid metastatic nodule associated with an omolateral internal jugular neoplastic thrombosis is presented together with a review of the literature on this matter. Renal cell carcinomas (RCC) are known to metastasize to all organs. These hypervascularized tumours are associated with multiple arteriovenous shunts where hemodynamic factors play a role in the seeding and subsequent growth of metastasis through the vascular route (1). Generally RCC diffuses in an unpredictable manner and can show a late recurrence as a notable feature. In 30% of cases metastasis are present at diagnosis. Late recurrence of RCC has been documented in the literature but not many studies address this topic. Differences are reported among the subtypes (clear cell, papillary and chromophobe renal carcinoma) that involve mainly the lungs, bone, lymph nodes and liver as secondary sites, whether synchronic or metachronic (2, 3). Gastric or duodenal metastases from clear cell renal carcinoma are exceptional (0.2 and 0.7% ) (4). Some of them can also metastasize to the brain and skin. Unusual sites are the ocular area, renal graft, suprarenal space and penis (5). The involvement of head and neck regions accounts for 8 to 14% of all secondaries (6, 7). Intrathyroid involvements are very rare, even though the thyroid is the second most vascularised organ following the adrenal gland. Cases of secondary thyroid cancer which require thyroid surgery are few (8). A clinical distinction of malignant thyroid tumors is often difficult. Solitary metastasis in this gland occurs about 100-120 months from the date of nephrectomy. There is a clear survival benefit in selected cases (single thyroid metastasis of RCC) if a surgical approach to the thyroid metastases is chosen, but generally patients have a poor prognosis, with 50% 5-year survival rates, since the presence of a thyroid metastasis is often the expression of a systemic disease. The knowledge of these atypical sites in patients with a past history of RCC allows an earlier diagnosis and treatment which could change the evolution of the illness.