Florid Squamous Metaplasia and Keratin Cyst Formation in Palatal Minor Salivary Gland Tumor: A Diagnostic Challenge.
Pleomorphic adenoma (PA) is a benign epithelial neoplasm of salivary glands. It is the most common salivary gland tumor which accounts for 54 65% of all salivary gland neoplasias and 80% of the benign salivary gland tumors. It mostly affects the parotid gland, followed by the submandibular gland and the minor salivary glands. Myoepithelial cell, being capable of dedifferentiation, metaplasia and transdifferentiation has a key role in the genesis of these tumors. The histopathologic picture may show squamous, mucous, and sebaceous and oncocytic metaplasia, sometimes with the formation of extensive keratin filled cysts lined by squamous epithelium. Metaplastic process is mainly triggered by trauma and probable etiology is ischemia. Extensive metaplasia can be mistaken for malignancy either mucoepidermoid carcinoma or squamous cell carcinoma. An unusual case of pleomorphic adenoma presented as a solitary intraoral palatine mass in a 62 year old male is reported here in which extensive squamous metaplasia and keratin cyst formations was evident microscopically.