A 58-year-old male smoker with a history of hypertension is found to have an incidental renal mass on contrast-enhanced CT. The tumor is described as a well-circumscribed, golden-yellow lesion with extensive areas of hemorrhage and necrosis, as shown in the diagram marked **B**. Which of the following best describes the origin and epidemiological significance of this lesion?
A. Arises from the distal convoluted tubule and is the second most common renal malignancy after Wilms tumor
B. Arises from the transitional epithelium of the renal pelvis and is the most common cause of hematuria in elderly patients
C. Arises from the proximal convoluted tubular epithelium and accounts for approximately 85% of primary renal malignancies in adults
Arises from the collecting duct and is associated with the best overall prognosis among renal tumors
D.
Explanation
Why option 1 is correct
The lesion marked B is renal cell carcinoma (RCC), clear cell type, characterized by its golden-yellow appearance with hemorrhage and necrosis. RCC arises from the proximal convoluted tubular epithelium and is the most common primary malignant tumor of the kidney in adults, accounting for approximately 85% of all renal cancers and 2–3% of all adult malignancies. The clear cell subtype (75–80% of RCC) results from VHL gene inactivation, leading to accumulation of lipids and glycogen that produce the characteristic golden-yellow gross appearance. Smoking (as in this patient) increases RCC risk 2-fold, and hypertension is another established risk factor.
Why each distractor is wrong
Option 2: While some renal tumors do arise from the distal tubule, RCC arises from the proximal tubule, not distal. Additionally, RCC is the most common, not second most common, renal malignancy; Wilms tumor is primarily a pediatric tumor and is not the leading renal cancer in adults.
Option 3: Collecting duct carcinoma is a rare and aggressive subtype of RCC with the worst prognosis, not the best. Chromophobe RCC (5% of cases) has the best prognosis among RCC subtypes. Collecting duct tumors do not present with the classic golden-yellow appearance.
Option 4: Transitional cell carcinoma (urothelial carcinoma) arises from the transitional epithelium of the renal pelvis and ureter, not the renal parenchyma. It is a distinct entity from RCC and accounts for only 5–10% of renal malignancies. The gross appearance and histology differ significantly from the clear cell RCC shown in the diagram.
