Solution: This patient has a complex cystic left renal mass that is concerning for renal cell carcinoma. In addition, he has bilateral pulmonary cysts. This combination of findings is concerning for the possibility of Birt-Hogg-Dube Syndrome. These patients with also have skin findings, specifically fibrofolliculomas, and will often have a history of spontaneous pneumothorax. They can also have oncocytomas in the kidney as well as RCC.