Metastases to the thyroid gland rare and >50% are from RCC, being diagnosed up to 20 years after nephrectomy. 2 patients underwent thyroidectomy in 2015 and 2019 in our center for renal metastases misdiagnosed with thyroidal goiter.

C.I.(F,78y) underwent left nephrectomy in Jan2012 for RCC; a new onset 10mm right thyroid nodule (Tir2 in 2013) was found at follow-up US and, due to increasing size (20mm), in 2015 new FNAC was performed, but twice inadequate Tir1. B.C.(M,73y) underwent left nephrectomy for RCC. In Sept2018; at follow-up US, 2 right confluent thyroid nodules (30mm) were spotted, resulting twice Tir1 at FNAC. At the TC in Jan2019, the nodules were increased (40mm).

In Jan2015, C.I. underwent total thyroidectomy; histopathological examination showed a right RCC metastasis. Other distant metastases were spotted in the following years and patient was treated with sunitinib, nivolumab and cabozantinib and the disease is finally stable. B.C. underwent total thyroidectomy in Sept2019; at the histopathological examination: right RCC metastasis. He was treated with sunitinib, achieving complete disease remission.

Overall survival of metastatic RCC is significantly increased in the recent years thanks to new systemic therapies. In common practice, presurgical diagnosis of metastases to the thyroid is difficult, and history of previous RCC should always be reported to the pathologist. In both cases the final diagnosis changed disease stage and therapeutic approach; both patients are alive at respectively 8y and 3y follow-up.