Case Report: Site-specific therapy guided by the 90-gene expression assay in cancer of unknown primary: lenvatinib plus camrelizumab for occult renal cell carcinoma.

Cancer of unknown primary (CUP) is primarily treated with empirical chemotherapy, but clinical outcomes remain unsatisfactory. We present the case of a 62-year-old male with asymptomatic left supraclavicular lymphadenopathy. Fine-needle aspiration revealed metastatic poorly differentiated carcinoma. Comprehensive evaluation, including contrast-enhanced computed tomography (CT), fluorodeoxyglucose positron emission tomography/CT (FDG-PET/CT), nasopharyngoscopy, and gastroscopy, failed to identify a definite primary tumor, leading to a diagnosis of CUP. Initial empirical chemotherapy with liposomal paclitaxel and nedaplatin showed limited efficacy and was complicated by grade 3 treatment-related adverse events (TRAEs), resulting in discontinuation due to poor tolerability. Subsequently, a core needle biopsy was performed. Immunohistochemistry suggested metastatic renal cell carcinoma (RCC). A 90-gene expression assay identified the kidney as the most likely primary site, with a similarity score of 82.6. The regimen was then switched to site-specific therapy with lenvatinib plus camrelizumab. The patient tolerated treatment well, experiencing only grade 1 TRAEs. Follow-up contrast-enhanced CT scans demonstrated significant lesion regression (33.1% and 69.6% reductions at 2 and 4 months, respectively), achieving a best response of partial response (PR). In conclusion, the combination of lenvatinib and camrelizumab demonstrated a favorable short-term response and acceptable tolerability in this patient, and renal-like CUP represents a distinct favorable CUP subset.