Liver Metastases of Unknown Primary Renal Cell Carcinoma Treated With Immune Checkpoint Inhibitors Plus Tyrosine Kinase Inhibitors: A Case Report and Literature Review

Background/Aim: Renal cell carcinoma (RCC) constitutes approximately 3% of all cancers. More than 60% of RCCs are detected incidentally; one-third of patients present with regional or distant metastases, and another 20-40% of patients develop metastases after radical nephrectomy. RCC can metastasize to any organ. In contrast, metastatic RCC (mRCC) without evidence of a primary tumor is extremely rare, with only a few reported cases. Case Report: We present a case of mRCC that initially presented with multiple liver and lymph node metastases but no primary renal lesion. An impressive response to treatment was achieved with a combination of immune checkpoint inhibitors and tyrosine kinase inhibitors. A clinical, radiological, and pathological diagnostic strategy, particularly in the context of a multidisciplinary team, are crucial for reaching a definitive diagnosis. This approach allows to select the appropriate treatment, making a huge difference for a mRCC due to its resistance to standard chemotherapy. Conclusion: There are currently no guidelines available for mRCC without primary tumor. Nevertheless, a combination of TKI and immunotherapy could be the optimal first-line treatment if systemic therapy is required.