Keratinizing pleomorphic adenoma: An unusual case report.

Pleomorphic adenoma (PA) is the most common benign tumor of major or minor salivary glands. PA exhibits a great histological diversity, such as differentiation into oncocytic, sebaceous, mucinous, squamous, chondroid, osseous or adipose cells. Squamous metaplasia rarely results in the formation of extensive keratin-filled cyst lined by squamous epithelium. Extensive squamous metaplasia can be mistaken for malignancy, including mucoepidermoid carcinoma and squamous cell carcinoma. Here, we report a case of slowly enlarging PA with extensive squamous metaplasia and keratin cyst formations in a minor salivary gland in hard palate and discuss its microscopic features.