A Rare Case of Missing Primary in Metastatic Renal Cell Carcinoma.

Renal cell carcinoma (RCC) can present with a myriad of clinical symptoms and signs. It is also notorious for its initial presentation with distant metastasis. We report a case of a 42-year-old male diagnosed with papillary RCC (PRCC) presenting with pleural and nodal metastases in the absence of a radiographically-detected tumor primary. PRCC was diagnosed on immunohistochemical analysis of the tissue from the pleura and mediastinal lymph nodes and confirmed by gene expression profiling studies. As per treatment guidelines for metastatic RCC, the patient was started on sunitinib with evidence of disease progression after two cycles and palliative care approach was recommended due to rapidly declining performance status. Prospective data on the optimal management of metastatic PRCC are lacking, but drugs used are similar to the treatment of clear cell carcinomas (vascular endothelial growth factor (VEGF) tyrosine kinase inhibitors, mammalian target of rapamycin inhibitors) and checkpoint inhibitors. Further molecular study of these rare tumors is warranted to detect drivers of oncogenesis and identify targets for therapeutic intervention.