Lingual metastasis as the first presentation of clear cell renal cell carcinoma: Report of a rare case clinically mimicking a benign lesion

Metastases in the oral cavity are rare and frequently associated with widespread disease and poor prognosis. Clear cell renal cell carcinoma (ccRCC) is the most common subtype of renal cell carcinoma (RCC), known for its propensity for metastatic spread. The diagnosis of oral metastases from ccRCC is challenging, especially when the patient has no history of primary neoplasm. Herein, we reported a rare metastatic ccRCC in a 58-year-old female presenting clinically as a painless nodule on the tongue mimicking a benign lesion. Microscopically, the tumor showed a proliferation of clear cells organized in nests with a predominantly lobular arrangement. The dense connective tissue stroma was highly vascularized, exhibiting some areas with a hyalinized aspect. Immunohistochemistry showed focal positivity for pan-cytokeratin AE1/AE3 and strong positivity for CK8, CK18, epithelial membrane antigen (EMA), vimentin, and CD10. S-100 protein, HMB-45, CK7, and CK20 were negative. The definitive diagnosis was metastatic ccRCC. The treatment was initiated with sunitinib. However, the disease progressed, and the patient was submitted to palliative care. Despite the low survival rate of patients with metastases, the clinician's experience in identifying an oral metastatic lesion may reveal undiagnosed primary tumors and provide better prognosis and survival rates.