## Most Common Histological Subtype of RCC **Key Point:** Clear cell RCC (ccRCC) accounts for 70–80% of all renal cell carcinomas, making it the most common subtype by a significant margin. ### Histopathological Features of Clear Cell RCC - **Cytoplasm:** Abundant lipid and glycogen → clear appearance on H&E staining - **Architecture:** Nests and sheets of polygonal cells separated by delicate capillary network - **Nuclei:** Variable size and irregularity (Fuhrman grading) - **Vascularity:** Highly vascular with prominent hemangiopericytoma-like pattern ### Molecular Basis - **VHL gene mutation:** Present in ~80% of sporadic ccRCC [cite:Robbins 10e Ch 20] - Loss of chromosome 3p (where VHL resides) - Results in accumulation of HIF-1α → angiogenesis and tumour growth ### Comparative Frequency Table | Subtype | Frequency | Key Feature | Prognosis | |---------|-----------|-------------|----------| | Clear cell | 70–80% | Clear cytoplasm, VHL mutation | Intermediate | | Papillary | 10–15% | Papillary architecture, MET mutation | Generally better | | Chromophobe | 5–10% | "Vegetable cells", binucleate, pale cytoplasm | Best | | Collecting duct | <1% | Aggressive, tubulopapillary | Worst | **Clinical Pearl:** Despite being the most common, clear cell RCC has intermediate prognosis. Chromophobe RCC, though rare, has the best 5-year survival (~90%), while collecting duct carcinoma is highly aggressive. **High-Yield:** The clear cytoplasm in ccRCC is due to lipid and glycogen content, not fat infiltration. This is a critical distinction in histology exams. ### Risk Factors for Clear Cell RCC - Smoking (1.5–2× risk) - Obesity - Hypertension - Chronic kidney disease - Von Hippel–Lindau (VHL) syndrome → nearly 100% lifetime risk **Mnemonic: VHL-CCC** — VHL mutations drive Clear Cell Carcinoma commonality.
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