Thyroid gland metastasis from renal cell carcinoma: a case series and literature review

Background: Renal cell carcinoma (RCC) is the most common malignancy that metastasises to the thyroid. This study aims to better understand the clinical characteristics of patients with thyroid metastasis from RCC. Methods: A retrospective case series of patients with thyroid metastasis from RCC between 2008 and 2020 from two tertiary centres were examined. MEDLINE and PubMed database searches were performed to retrieve the relevant literature. Results: Fifteen patients (eight males) were identified, with a median age of 57.0 (interquartile range (IQR) 51.0–63.0) at time of RCC diagnosis. Median time to thyroid metastasis was 92.0 months (IQR 40.0–156.0), with 12 (80.0%) patients undergoing thyroidectomy within 2 months of diagnosis. No patients developed post-operative complications or local thyroid recurrence. The two most common non-thyroid metastatic sites in this case series are lungs and bone (five patients, respectively; 33.3%) and pancreas (four patients; 26.7%). Ten (66.6%) patients underwent systemic chemotherapy, and five (33.4%) patients underwent radiotherapy for other sites of metastasis. Median survival following thyroid metastasis was 54.0 months (IQR 15.0–100.0). The literature review was conducted through MEDLINE and PubMed database searches, and 30 papers were considered relevant to this review. Results from our study are comparable to those reported in the literature. Conclusion: Thyroid metastases can occur long after nephrectomy and portends a better prognosis. To prevent development of central neck disease, thyroidectomy should be considered.