Tumorous lesions of the oral cavity are mostly of dental or local pathological origin. On occasion, they may have a distant origin outside the field of dentistry. Under certain circumstances, this can lead to serious consequences. Renal cell carcinomas are known for their frequent metastasis to the lungs, liver, bones, and brain. Metastases to the oral cavity are rare. Case report: A 68-year-old woman with previously unknown renal cell carcinoma is presented. By biopsy of a suspicious lesion, an intraoral clear cell carcinoma was diagnosed. In the following tumor staging, a metastasizing clear cell renal cell carcinoma was identified as the focus and a systemic therapy was initiated. Summary: This case report exemplarily shows the importance of timely histological verification of each new intraoral lesion. Under certain circumstances, a diagnosis of a surprising and potentially life-threatening condition may be made in time to initiate adequate treatment.