A 40-year-old male complains of hematuria and an aching pain in his flank. Laboratory data show normal BUN, creatinine, and electrolytes. Hemoglobin is elevated at 18 g/dL and serum calcium is 11 mg/dL. A solid renal mass is found by ultrasound. The most likely diagnosis is

Renal carcinoma is twice as common in men as women and tends to occur in the 50- to 70-year age group. Many patients present with a hematuria or flank pain, but the classic triad of hematuria, flank pain, and a palpable flank mass occurs in only 10 to 20% of patients. Paraneoplastic syndromes such as erythrocytosis, hypercalcemia, hepatic dysfunction, and fever of unknown origin are common. Surgery is the only potentially curable therapy; the results of treatment with chemotherapy or radiation therapy for nonresectable disease have been disappointing. Interferon a and interleukin 2 produce responses (but no cures) in 10 to 20% of patients. The prognosis for metastatic renal cell carcinoma is dismal.