**Core Concept**
A Warthin's tumor is a benign neoplasm of the parotid gland, characterized by the proliferation of oncocytes and lymphocytes. It is a type of salivary gland tumor that is often associated with smoking. The exact pathogenesis of Warthin's tumor is not well understood, but it is believed to involve the abnormal proliferation of oncocytes, which are cells that are rich in mitochondria.

**Why the Correct Answer is Right**
Warthin's tumor is a distinct entity that is typically composed of two types of cells: oncocytes and lymphocytes. The oncocytes are large cells with abundant granular cytoplasm, while the lymphocytes are small cells that are scattered throughout the tumor. The presence of oncocytes and lymphocytes is a hallmark of Warthin's tumor, and it is often used as a diagnostic criterion. The tumor is typically found in the parotid gland, and it is often associated with smoking.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the histological features of Warthin's tumor. While some salivary gland tumors may be composed of oncocytes, not all tumors with oncocytes are Warthin's tumors.
**Option B:** This option is incorrect because it does not accurately describe the clinical presentation of Warthin's tumor. While some salivary gland tumors may be painful, Warthin's tumor is typically painless.
**Option C:** This option is incorrect because it does not accurately describe the histological features of Warthin's tumor. While some salivary gland tumors may be composed of lymphocytes, not all tumors with lymphocytes are Warthin's tumors.

**Clinical Pearl / High-Yield Fact**
Warthin's tumor is often associated with smoking, and it is one of the few benign tumors that is more common in men than women. This is a useful fact to remember when approaching salivary gland tumors, as it can help guide the differential diagnosis.

**Correct Answer: C. A benign tumor of the parotid gland composed of oncocytes and lymphocytes.**