A 50-year-old man is found to have blood in his urine during a routine checkup. He is otherwise in excellent health, except for a mild microcytic, hypochromic anemia. An enlarged right kidney is found on X-ray examination, and CT scan reveals a renal mass of irregular shape, measuring 6 cm in diameter. Which of the following is the most likely diagnosis?

RCC is the most common cancer of the kidney, accounting for 90% of kidney cancers. Most cases of RCC are sporadic, but about 5% are inherited. The 5-year survival is 90% if the RCC has not extended beyond the renal capsule; survival drops to 30% if there are distant metastases. The tumor spreads most frequently to the lung and the bones. Oncocytoma and angiomyolipoma (choice A) are often difficult to differentiate from RCC by imaging techniques. Tumors such as nephroblastoma (choice C) and Wilms tumor (choice E) occur in the pediatric age group.Diagnosis: Renal cell carcinoma