Abstract: Objective To summarize and analyze the clinical features, diagnostic methods, treatment, and prognosis of patients with renal clear cell carcinoma(RCCC)that has metastasized to the nasal cavity and paranasal sinuses. Methods We conducted a retrospective review of the records of one patient with RCCC that had metastasized to the paranasal sinuses. We also performed a literature review and included 64 relevant studies published in Chinese and English from 1993 to 2020, including this case. A total of 76 patients with renal clear cell carcinoma that had metastasized to the paranasal sinuses were included, and their clinical manifestations, diagnosis, treatment methods, and prognosis were summarized. Results The 76 patients included 61 men and 15 women, with the most common symptoms being epistaxis in 58 patients and nasal obstruction in 25. The metastases were located in the nasal cavity(n=52), ethmoid sinus(n=41), and maxillary sinus(n=22). Twent-eight patients had sinonasal metastasis of renal clear cell carcinoma at first presentation. The delay between the diagnosis of the primary tumor and the diagnosis of metastasis to the sinonasal cavity ranged from 15 days to 27 years(mean, 46 months; median, 12 months). On CT and MRI, the lesions exhibited osteolysis and strong enhancement after contrast injection. The misdiagnosis rate was 22%. Immunohistochemistry was crucial for the correct diagnosis, and the most commonly used markers were CK, Vimentin, CD10, PAX8. Twenty-five patients(32.9%)underwent surgical management alone, 28 patients(36.8%)had surgical management combined with radiotherapy/chemotherapy/targeted therapy, 19 patients(25.0%)received targeted therapy alone and/or chemoradiotherapy, and 4 patients received no treatment. Follow-up data were available for 51 patients, and the duration of follow-up ranged from 1 month to 14 years(median, 12 months). There was a strong statistically significant association between surgery and a better prognosis(P<0.001). The overall survival was significantly better for patients whose duration between the primary tumor and metastasis was more than 4 months vs. no more than 4 months(P=0.008 7). There was no statistical difference in overall survival between patients who had sinonasal metastasis at first presentation of RCCC and those who had already been diagnosed with RCCC earlier(P=0.14), an isolated metastasis rather than multiple metastases(P=0.1), and surgery alone rather than surgery combined with radiotherapy(P=0.52). Conclusion Metastatic renal clear cell carcinoma to the nasal cavity and paranasal sinuses is rare. It mainly affects elderly males and can be diagnosed at the initial presentation of RCCC or long after treatment of the primary tumor. The most common symptoms are epistaxis and nasal obstruction. On CT and MRI, the lesions exhibit strong enhancement after contrast injection. The diagnosis depends on pathology and immunohistochemistry. It can easily be misdiagnosed as hemangioma. Surgical resection is the main treatment, and nasal endoscopic surgery after vascular embolization is recommended as it can improve the prognosis of the patients. Patients who cannot undergo surgery can undergo targeted therapy or chemoradiotherapy, with a poor overall prognosis.

Key words: Renal clear cell carcinoma, Nasal cavity, Paranasal sinuses, Metastases, Hemangioma