**Core Concept:** Pleomorphic adenoma is a benign tumor of the salivary gland, primarily composed of both epithelial and myoepithelial cells. The term "pleomorphic" refers to the variable and diverse histological appearance of the tumor cells. These tumors are slow-growing and can occur in any salivary gland, but are most common in the parotid gland.

**Why the Correct Answer is Right:** The correct answer is B, as it is the only statement that is not true about pleomorphic adenoma. Pleomorphic adenomas are benign tumors, meaning they are not malignant and do not have the potential to spread to other parts of the body. Statement B claims that pleomorphic adenomas are malignant, which is incorrect.

**Why Each Wrong Option is Incorrect:**
A. Pleomorphic adenoma is a benign tumor, not a malignant one. Therefore, statement A is incorrect.
C. Pleomorphic adenomas are composed of both epithelial and myoepithelial cells, which makes them distinct from mixed tumors. Statement C is incorrect.
D. Pleomorphic adenomas are slow-growing, non-invasive benign tumors, not "invasive malignant tumors." Statement D is incorrect.

**Clinical Pearl / High-Yield Fact:** Understanding the distinct histopathological features of pleomorphic adenoma is essential for accurate diagnosis and patient management. This knowledge is particularly important for medical professionals dealing with salivary gland tumors, such as pathologists, oncologists, and head and neck surgeons.

**Correct Answer:** B. Pleomorphic adenoma is not malignant (benign).