A case of renal cell carcinoma metastasized to the sublingual gland

Renal cell carcinoma (RCC) tends to metastasize hematogenously to organs throughout the body.RCC often metastasizes to the lungs and bones, but metastasis to the oral region is uncommon.In the oral cavity, the usual metastatic sites are the tongue and jawbone, and there are a few cases involving the salivary glands.Metastasis to the sublingual gland is extremely rare.Herein, we report a case of RCC that metastasized to the sublingual gland.The patient, a 74-year-old woman, was diagnosed with advanced RCC with distant metastasis to the brain, pancreas, etc. at another hospital.After undergoing radiation therapy for the metastatic brain tumor, she was transferred to the medical oncology department of our hospital.When she visited the department of dentistry and oral surgery for oral management following the initiation of chemotherapy, we found a 25 mm diameter mass in the right floor of the mouth.MRI showed a mass lesion with slightly high signals in the right sublingual gland region on T1 and T2 weighted images.An incisional biopsy revealed proliferation of tumor cells with pale eosinophilic cytoplasm and hyperchromatic nuclei, leading to a pathological diagnosis of metastasis of clear cell RCC to the sublingual gland.Subsequently, chemotherapy with cabozantinib, a molecular targeted drug, was initiated.Both the primary and metastatic tumors had shrunk on imaging findings within six months.The tumors had not grown during the one year after the initiation of treatment.