**Core Concept**
Paraneoplastic syndromes are clinical disorders caused by the presence of a tumor, but not due to direct local effects of the tumor cells. Renal cell carcinoma (RCC) is a type of kidney cancer that can cause various paraneoplastic syndromes due to the production of hormones or other substances by the tumor cells.

**Why the Correct Answer is Right**
Cushing syndrome, characterized by excess cortisol production, is not typically associated with RCC. The correct paraneoplastic syndromes associated with RCC include polycythemia (due to erythropoietin production), hypercalcemia (due to parathyroid hormone-related protein production), and hypertension (due to various mechanisms, including renin production). Cushing syndrome is more commonly associated with other types of tumors, such as small cell lung cancer or pituitary adenomas.

**Why Each Wrong Option is Incorrect**
**Option A:** Polycythemia is a known paraneoplastic syndrome associated with RCC, caused by the production of erythropoietin by the tumor cells.
**Option B:** Hypercalcemia is also a recognized paraneoplastic syndrome associated with RCC, resulting from the production of parathyroid hormone-related protein by the tumor cells.
**Option C:** Hypertension is a possible paraneoplastic syndrome associated with RCC, due to various mechanisms, including the production of renin by the tumor cells.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize the paraneoplastic syndromes associated with RCC, as they can be the presenting symptoms of the disease, and prompt diagnosis and treatment of the underlying tumor can improve patient outcomes.

**✓ Correct Answer: D. Cushing syndrome**