Oral metastatic tumor (renal cell carcinoma) in maxillary gingiva: A case report and systematic review

Background and objective: Oral metastases are rare. We experienced a case of oral metastasis of renal cell carcinoma (RCC) and discussed its characteristics with a systematic review to survey the literature for useful features for the diagnosis of oral metastatic RCC. Methods: A systematic review was conducted according to the PRISMA 2020 statement. An electronic search was performed using three databases and the literature of cases of renal cancer metastasis to the jawbone and gingiva. Results: Thirty studies were identified (male-to-female ratio, 2.75:1). The site of metastasis was the jawbone in 66.7 % (mandible, 60 %; maxilla, 6.7 %) and the gingiva in 30 %. Clinical symptoms were a mass in 86.7 % and hypoesthesia in 23.3 %. A total of 76.7 % of oral metastases were clear cell type. In our case, the male patient showed a mass in the maxillary gingiva without hypoesthesia. Metastatic clear cell RCC was suspected by an oral biopsy, which was confirmed on clinical examinations, including a renal biopsy. Conclusion: Oral metastases are rare, and the clinical and imaging findings for oral metastases of RCC are wide-ranged with low specificity, depending on the metastatic site. It is necessary to fully understand the key points in histopathological differentiation. Because the clinician plays a fundamental role in the early diagnosis of oral cancer and the identification of metastatic lesions, awareness of the possibility of rare tumors as in this study can facilitate an accurate preoperative diagnosis and the planning of appropriate treatment.