Abstract
Tumors of the minor salivary glands are an important area in oral surgery and pathology. A relatively high proportion of these are malignant, especially in the tongue, floor of the mouth and retromolar area. Although, as observed in major glands, pleomorphic adenoma (PA) and mucoepidermoid carcinoma (MeC) are the most common benign and malignant minor salivary gland tumors, respectively, some tumors such as canalicular adenoma, ductal papillomas, polymorphous low-grade adenocarcinoma and clear cell carcinoma NOS occur exclusively in minor salivary glands, while high-grade malignant tumors, for example salivary duct carcinoma and oncocytic carcinoma, are rare. Small parts of MeC arise in the jaws (central MeC), suggestive of odontogenic origin. Intraoral tumors are susceptible to trauma or inflammation-related ulceration. Histopathologically, benign minor salivary gland tumors have occasionally incomplete capsules and are juxtaposed against surrounding tissues. Furthermore, inflammation may cause various pseudomalignant changes of the tumors. As adenoid cystic carcinoma (AdCC) is common in minor salivary glands and shares architectural and cellular differentiating characteristics with PA, it is sometimes difficult to distinguish between these neoplasms in small biopsy specimens. Activity of cellular proliferation and immunolocalization of S100 protein may be helpful in the differential diagnosis. In AdCC, down-regulation of p27 protein caused by ubiquitin-mediated degradation by S-phase kinase-associated protein 2 (Skp2) overexpression is closely correlated with metastasis and low survival rate, indicating that reduced expression of p27 and overexpression of Skp2 could be good predictive markers of AdCC.
The clinical and pathological differentiation from tumor-like lesions including necrotizing sialometaplasia and adenomatous hyperplasia is also important.
