Tumors are poorly circumscribed with an infiltrative border, including extracapsular extension beyond the salivary gland.
FIRST PARAGRAPH: Adenoid cystic carcinoma (ACC) is a malignant epithelial salivary gland tumor with myoepithelial and ductal differentiation. Salivary gland tumors account for only about 5% of all head and neck carcinomas, with ACC the fourth most common salivary gland malignancy. ACC has a 3:2 female-to-male ratio. Patients tend to be adults, with a peak clinical presentation in the sixth decade. The tumors are found most frequently in the parotid gland but are also found in the palate, tongue, lip, and other sites in the upper aerodigestive tract and the rest of the body.