American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What histological feature is commonly associated with pleomorphic adenoma?

1. Mixed cellularity

2. Keratinization

3. Necrosis

4. High-grade atypia

The correct answer is: Mixed cellularity

Pleomorphic adenoma is characterized by its mixed cellularity, which is a distinctive histological feature. This tumor is a type of benign salivary gland neoplasm, most commonly found in the parotid gland. Histologically, pleomorphic adenomas exhibit a variety of cellular components including both epithelial and mesenchymal elements such as glandular cells and myoepithelial cells, as well as stroma that can be fibrous or myxoid. The term "pleomorphic" itself signifies the existence of multiple forms or types of cells within the tumor, reflecting its complex architecture. The presence of mixed cellularity is crucial in differentiating pleomorphic adenomas from other types of neoplasms. While some tumors can exhibit keratinization or necrosis, these features are not typically associated with pleomorphic adenoma in its benign form. High-grade atypia would suggest a malignant process, which is not characteristic of pleomorphic adenomas unless they undergo malignant transformation. Thus, the histological feature of mixed cellularity is central to understanding the nature and classification of pleomorphic adenomas.