**Core Concept**
Clear cell carcinoma of the kidney, also known as renal cell carcinoma (RCC), is the most common type of kidney cancer in adults. It originates from the proximal convoluted tubule cells of the renal cortex. The tumor cells exhibit clear cytoplasm due to the high content of lipids and glycogen.

**Why the Correct Answer is Right**
Clear cell RCC typically exhibits several characteristic features, including:
- Clear cytoplasm due to the accumulation of lipids and glycogen
- High nuclear-to-cytoplasmic ratio and pleomorphic nuclei
- Presence of large, eosinophilic nucleoli
- Loss of E-cadherin and beta-catenin expression, leading to epithelial-to-mesenchymal transition (EMT)
- Tumor cells often express carbonic anhydrase IX (CA IX), which contributes to the tumor's acidic microenvironment

**Why Each Wrong Option is Incorrect**
**Option A:** Clear cell carcinoma can indeed exhibit a mix of clear and granular cells, but this is not a defining feature that distinguishes it from other types of RCC.
**Option B:** Clear cell RCC is often associated with mutations in the VHL gene, which leads to the accumulation of hypoxia-inducible factor-alpha (HIF-alpha) and subsequent upregulation of CA IX and other hypoxia-responsive genes.
**Option C:** While clear cell RCC can exhibit a mix of clear and granular cells, the presence of large, eosinophilic nucleoli is a characteristic feature of this tumor type.

**Clinical Pearl / High-Yield Fact**
Clear cell RCC is the most common type of kidney cancer, accounting for approximately 70-80% of all RCC cases. It tends to present with hematuria, flank pain, and a palpable abdominal mass.

**Correct Answer: A.**