Most common variant of RCC is
**Core Concept**
Clear cell renal cell carcinoma (RCC) is the most common variant of renal cell carcinoma, accounting for approximately 70-80% of all RCC cases. It arises from the proximal convoluted tubule of the kidney and is characterized by the presence of large, clear cells with abundant cytoplasm and minimal cellular nuclei.
**Why the Correct Answer is Right**
Clear cell RCC is the most common variant due to the mutation of the VHL gene, which leads to the accumulation of HIF-alpha and subsequent upregulation of vascular endothelial growth factor (VEGF). This results in increased angiogenesis and tumor growth. The clear cells are characterized by the presence of lipid-rich cytoplasm, which is due to the accumulation of lipids as a result of the metabolic alterations caused by the VHL mutation.
**Why Each Wrong Option is Incorrect**
**Option A:** Papillary RCC is the second most common variant of RCC, but it accounts for only 10-15% of cases. It is characterized by the presence of papillary structures and is often associated with mutations in the MET and TRAF3 genes.
**Option B:** Chromophobe RCC is a rare variant of RCC, accounting for only 5% of cases. It is characterized by the presence of large, pale cells with abundant cytoplasm and is often associated with mutations in the BHD gene.
**Option C:** Collecting duct RCC is a rare variant of RCC, accounting for only 1-2% of cases. It is characterized by the presence of cells that resemble those found in the collecting ducts of the kidney.
**Clinical Pearl / High-Yield Fact**
Clear cell RCC is more common in patients with a family history of the disease and those with a history of smoking. It is also associated with an increased risk of metastasis to the lungs, bones, and brain.
**Correct Answer: C. Chromophobe RCC is a rare variant of RCC, accounting for only 5% of cases. It is characterized by the presence of large, pale cells with abundant cytoplasm and is often associated with mutations in the BHD gene.**