What is the most likely diagnosis for a patient with a flank mass, microscopic hematuria, hypertension, and a history of smoking and gout?

Renal Cell Carcinoma

The most likely diagnosis is B: Renal cell carcinoma (RCC). This 45-year-old man presents with the classic triad of flank mass, hematuria, and back pain, combined with high-risk features including chronic smoking and age >40 years, all pointing toward RCC rather than the other options 1.

Clinical Reasoning

Why Renal Cell Carcinoma is Most Likely

• The classic triad of flank pain, palpable abdominal/flank mass, and hematuria—though now seen in <10% of cases—is most often associated with locally advanced or metastatic RCC when present 1.
• Smoking is a major risk factor for RCC development, and this patient's chronic smoking history significantly elevates his risk 1.
• Age 45 years places him in the typical demographic for RCC, which has peak incidence in middle-aged adults 1.
• Pallor suggests anemia, which can occur as a paraneoplastic manifestation of RCC or from chronic blood loss 1.
• Isolated microscopic hematuria with a flank mass in a patient >40 years with smoking history represents high-risk features requiring complete urologic evaluation including upper tract imaging 1.

Why Other Diagnoses are Less Likely

Polycystic kidney disease (Option A):

• Typically presents with bilateral enlarged kidneys, not a unilateral flank mass 1.
• Usually diagnosed earlier in life or has family history 1.
• Would show multiple cysts on imaging, not a solid mass 1.

Renal tuberculosis (Option C):

• Would typically present with sterile pyuria (white blood cells without bacteria), not isolated hematuria 1.
• Usually accompanied by constitutional symptoms (fever, night sweats, weight loss) more prominent than in RCC 1.
• Requires specific risk factors (TB exposure, immunosuppression, endemic area) not mentioned here 1.

Hyperuricemic nephropathy (Option D):

• While this patient has gout, hyperuricemic nephropathy presents with renal insufficiency and elevated creatinine, not a palpable mass 1.
• Does not cause discrete flank masses 1.
• Would show bilateral kidney involvement with chronic changes, not a unilateral mass 1.

Immediate Diagnostic Workup Required

• Obtain multiphase CT urography with contrast to characterize the renal mass, assess for enhancement, and clinically stage the tumor 1, 2.
• Chest CT imaging is mandatory to evaluate for pulmonary metastases, as RCC commonly metastasizes to lungs 1.
• Complete metabolic panel including serum calcium (to detect hypercalcemia as paraneoplastic syndrome), liver function tests, and lactate dehydrogenase 1.
• Complete blood count to assess degree of anemia 1.
• Cystoscopy must be performed despite the presence of a renal mass, as age >60 years (he's 45, but with >10 pack-year smoking history) represents high risk for concomitant urothelial malignancy, and hematuria should never be attributed solely to the renal mass without excluding bladder pathology 1, 2.

Critical Clinical Pitfalls

• Never attribute hematuria solely to a renal mass without completing cystoscopy to exclude synchronous bladder cancer, particularly in smokers 2, 3.
• Do not delay imaging—the presence of a palpable flank mass with hematuria requires urgent cross-sectional imaging, as this presentation suggests locally advanced disease 1.
• Renal mass biopsy is NOT required before surgical planning when imaging strongly suggests RCC, though it may be considered if diagnosis is uncertain or for patients considering active surveillance 1.
• The hypertension may be tumor-related (renin secretion by RCC) rather than essential hypertension, and may resolve after nephrectomy 1.