Renal Cell Carcinoma Presenting as Pleural Effusion.

Renal cell carcinoma is well-known for its propensity to present in unusual ways, and renal cell carcinoma presenting as pleural effusion is extremely rare. Pleural effusion secondary to renal cell carcinoma constitutes only about 1% to 2% of all malignant pleural effusions. We report the case of a 34-year-old man with no significant past medical or surgical history who presented in the Emergency Department with dyspnea. Chest x-ray demonstrated right-sided pleural effusion; computed tomography (CT) reported right-sided effusion in the pleura with suspicious mass in the upper border of left kidney. CT-guided pleural tap was performed and cytology was positive for vimentin and common acute lymphocytic leukemia antigen (CD10), leading to the diagnosis of primary renal cell carcinoma presenting as unilateral pleural effusion. While lungs are the common site of metastasis, the presentation of renal cell carcinoma as pleural effusion or pleural metastasis without lung involvement is rare.