A 65-year-old male smoker with hypertension presents with painless gross hematuria for 3 weeks, right flank discomfort, and 6 kg unintentional weight loss over 3 months. Examination reveals a palpable right flank mass and a non-reducing left varicocele. Renal ultrasound demonstrates a 7 cm **solid, heterogeneous, predominantly hypoechoic mass** arising from the upper pole of the right kidney with internal echoes, areas of cystic necrosis, and distortion of the cortico-medullary architecture. Color Doppler shows internal vascularity. The contralateral kidney is normal.
The structure marked **A** in the diagram represents this solid heterogeneous renal mass. Which of the following is the most likely histologic subtype and its associated genetic abnormality?
A. Chromophobe RCC with BHD/folliculin gene mutation
B. Clear cell RCC with VHL gene mutation on chromosome 3p25
Collecting duct carcinoma with TP53 mutation
C.
D. Papillary RCC type 1 with MET gene mutation
Explanation
Why Clear cell RCC with VHL gene mutation on chromosome 3p25 is right
Clear cell RCC accounts for approximately 75% of all renal cell carcinomas and is the most common histologic subtype. The classic imaging appearance of a solid, heterogeneous, predominantly hypoechoic mass with internal vascularity (as shown by the structure marked A and confirmed by Color Doppler) is typical of clear cell RCC. Clear cell RCC arises from the proximal tubular epithelium and is strongly associated with VHL (von Hippel-Lindau) gene mutations on chromosome 3p25, which lead to accumulation of HIF and angiogenic factors, resulting in the characteristic internal vascularity and heterogeneous enhancement seen on imaging. The patient's risk factors (smoking, hypertension, age 60–70) and presentation (hematuria, flank pain, palpable mass, weight loss) are classic for RCC, and the imaging characteristics of the mass marked A are most consistent with clear cell histology. [NCCN Kidney Cancer Guidelines; AUA Renal Mass Guidelines]
Why each distractor is wrong
Papillary RCC type 1 with MET gene mutation: Papillary RCC accounts for only 10–15% of renal cell carcinomas, making it significantly less common than clear cell RCC. While MET mutations are associated with hereditary papillary RCC and type 1 papillary RCC, this subtype is not the most likely diagnosis given the epidemiologic frequency and imaging presentation of the mass marked A.
Chromophobe RCC with BHD/folliculin gene mutation: Chromophobe RCC represents only ~5% of renal cell carcinomas. Although it is associated with Birt-Hogg-Dubé syndrome and folliculin mutations, the imaging appearance and frequency make this an unlikely diagnosis for the solid heterogeneous mass marked A in this clinical scenario.
Collecting duct carcinoma with TP53 mutation: Collecting duct carcinoma is a rare subtype of RCC and is associated with a much more aggressive clinical course and poor prognosis. It is not among the common histologic subtypes and would not be the most likely diagnosis for a 7 cm solid heterogeneous mass in a patient with classic RCC presentation.
High-YieldNEET PG
Clear cell RCC (~75% of cases) + VHL mutation + internal vascularity on imaging = most common RCC subtype with characteristic genetic abnormality.
[NCCN Kidney Cancer Guidelines; AUA Renal Mass Guidelines]
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