Rare metastatic sites in three patients with RAI-refractory differentiated thyroid cancer (DTC).

[PURPOSE] While the majority of patients with differentiated thyroid cancer (DTC) have favourable outcomes, less than 5% may have metastatic disease that is refractory to radioiodine (RAI) treatment. Distant metastases from thyroid cancer usually involve the lungs and bones. However, it is essential to accurately identify and treat rare sites of metastasis.

[METHODS] In this report, we present three cases of rare metastatic sites originating from RAI-refractory DTC. The first patient had a cystic calcaneous metastasis, the second patient developed bilateral metachronous renal metastases, and the third patient presented with a large thigh metastasis, which was later followed by a large pelvic mass.

[RESULTS] None of the patients had a targetable mutation. A multidisciplinary therapeutic approach was implemented for their treatment, incorporating both local and systemic therapies.

[CONCLUSION] Managing cases with unusual metastases can be particularly challenging, especially in patients with advanced disease. The combination of local and systemic treatments is crucial, as it may help prolong survival.