## **Core Concept**
Brain metastases are the most common intracranial tumors in adults, arising from the spread of cancer from other parts of the body. The metastatic process involves the hematogenous spread of cancer cells to the brain. Different primary cancers have different propensities to metastasize to the brain.

## **Why the Correct Answer is Right**
The correct answer, **C. Cerebral hemispheres**, is the most common site for brain metastases. This is because the cerebral hemispheres have a large volume of blood flow and a high oxygen tension, which makes them a common site for metastatic deposition. The majority of brain metastases are located at the junction of the gray and white matter, where the caliber of blood vessels abruptly decreases, facilitating the lodging of tumor cells.

## **Why Each Wrong Option is Incorrect**
* **Option A:** While the **cerebellum** can be a site for metastasis, it is less common compared to the cerebral hemispheres.
* **Option B:** The **brainstem** is a rare site for metastasis due to its relatively lower blood flow and the presence of the blood-brain barrier.
* **Option D:** The **meninges** can be involved by metastatic cancer, but this is typically seen as leptomeningeal carcinomatosis rather than a distinct metastatic site like the cerebral hemispheres.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the most common primary cancers that metastasize to the brain are lung, breast, and melanoma. Metastases are usually multiple and often located at the gray-white junction.

## **Correct Answer:** C. Cerebral hemispheres.