Renal cell carcinomas (RCCs), either as benign or malignant renal tumors, have obscure signs and symptoms, are clinically occult, and often are diagnosed by primary care providers (PCPs) in the initial workup of a classical triad of flank pain, palpable abdominal renal mass, and hematuria. In addition, renal masses are nowadays more frequently seen in the evaluation of nonurologic abnormalities on sonograms, CT scanning, and MRI. This chapter focuses on the epidemiology, pathology, clinical and radiographic presentation, staging methods, and surgical and systemic treatment modalities of primary renal neoplasms. Renal oncocytoma is the most common benign tumor that appears as an enhancing renal mass on cross-sectional imaging; it is presumed to be RCC until surgical excision, representing challenges in preoperative diagnosis for the urologist. The treatment of a patient with a solitary renal mass and a history of cancer with no known metastasis is more controversial.