## **Core Concept**
The submandibular gland is one of the major salivary glands, and like other salivary glands, it can be affected by various types of tumors. Salivary gland tumors can be benign or malignant, with a wide range of histological types. The submandibular gland is less commonly affected by tumors compared to the parotid gland but has a higher proportion of malignant tumors.

## **Why the Correct Answer is Right**
The correct answer, **Pleomorphic adenoma**, is the most common tumor of the submandibular gland, although it is more frequently found in the parotid gland. Pleomorphic adenomas, also known as benign mixed tumors, are characterized by their diverse cellular components, including both epithelial and mesenchymal elements. They are known for their slow growth and are typically benign, but they can undergo malignant transformation if left untreated.

## **Why Each Wrong Option is Incorrect**
- **Option A: Warthin's tumor** - This is a type of benign tumor that primarily affects the parotid gland, not the submandibular gland. It is less common in the submandibular gland.
- **Option C: Mucoepidermoid carcinoma** - This is a type of malignant tumor that can occur in the salivary glands, including the submandibular gland. While it is a significant tumor type in this gland, it is not the most common tumor overall.
- **Option D: Adenoid cystic carcinoma** - This is another type of malignant tumor that can occur in the submandibular gland. It is known for its perineural invasion but is not the most common tumor of the submandibular gland.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while pleomorphic adenoma is the most common tumor of the salivary glands overall, the submandibular gland has a higher proportion of malignant tumors compared to the parotid gland. Therefore, any tumor in the submandibular gland should be approached with a high index of suspicion for malignancy.

## **Correct Answer:** B. Pleomorphic adenoma