Intercalated duct reserve cells are the source for adenoid cystic carcinomas, acinic cell carcinomas, pleomorphic adenomas, malignant mixed tumors, and terminal duct adenocarcinomas. Excretory duct reserve cells are the source for mucoepidermoid carcinomas, squamous cell carcinomas, and salivary duct carcinomas. Histopathologic diagnosis is a key factor in predicting the clinical course of malignant salivary tumors. The correlation of histopathology with biologic behavior has prompted the classification of the common malignancies into two groups. Low-grade lesions include acinic cell carcinoma, terminal duct adenocarcinoma, papillary adenocarcinoma, and clear cell carcinoma.
Examples are mucoepidermoid carcinoma and adenoid cystic carcinoma.
Histopathologic diagnosis and grading, therefore, play important roles in determining the extent of treatment for patients with salivary gland malignancies. The relative frequency of the histologic subtypes varies among the different salivary glands. Acinic cell carcinoma, other adenocarcinomas, and adenoid cystic carcinoma follow in decreasing order of frequency within the parotid gland. Mucoepidermoid carcinoma is the next most common submandibular and sublingual salivary cancer, followed by the adenocarcinomas. The adenocarcinomas are the second most common malignancy of the minor salivary glands.