Overview of Salivary Gland Cancer
Salivary gland cancers account for approximately 5% of all head and neck malignancies. The major salivary glands consist of the parotids, located just in front of the ears, the submandibulars, located just under the jawline, and the sublingual glands, which are located in the floor of the mouth. The minor salivary glands are located throughout the upper aerodigestive tract, mostly in the oral and nasal cavities and throughout the paranasal sinuses.
Most salivary glands tumors occur in the parotid glands.
Several risk factors are associated with the development of salivary gland cancers, but more research must be done before it can be said conclusively that they are proven causes. These factors include ionizing radiation, wood dust inhalation and genetic or familial predisposition to the disease. Pathologically, tumors arising in the salivary glands may be either benign or malignant neoplasms.
Benign tumors include benign mixed tumors, Warthin's tumor (benign papillary cystadenoma), monomorphic adenoma and benign lymphoepithelial lesions.
Malignant tumors include mucoepidermoid carcinoma, adenoid cystic carcinoma, adenocarcinoma, malignant mixed tumor, acinic cell carcinoma and epidermoid carcinoma:
- Warthin's tumor is a slow-growing, cystic tumor that almost always occurs in older men.
- Monomorphic adenomas are a group of benign lesions with a variety of growth patterns. These lesions usually are found in the parotid glands.
- Benign lymphoepithelial lesions include a wide range of cystic changes that share the common denominator in atypical lymphoid hyperplasia. Hyperplasia refers to a proliferation of cells that is non-neoplastic. These changes are found often in patients infected with HIV.
- Benign mixed tumor is the most common tumor of the major salivary glands. Pathologically, it is characterized by slow growth and few symptoms.
- Acinic cell cancers are rare, accounting for less than 10% of all salivary gland tumors. They tend to arise in the parotid and submandibular glands, and are considered low-grade malignancies.
- Mucoepidermoid cancer is unique in that the tumors it produces can vary in aggressiveness from low-grade and slow growing to high-grade and rapidly growing. It occurs more frequently than any other malignancy of the major salivary glands.
- Adenocarcinomas are most frequently found in the minor salivary glands of the nose and paranasal sinuses. They do, however, account for 15% of malignancies of the parotid and 10% of malignancies of the submandibular glands. Squamous cell cancers are uncommon in salivary gland tissue. In many cases they originate not in the parotid itself, but stem from metastases originating elsewhere in the head and neck.
- Malignant mixed tumors make up approximately 15% and 12% of parotid and submandibular neoplasms respectively. The disease typically is characterized by slow, protracted growth.
- Adenoid cystic carcinomas account for 25% of malignant salivary gland tumors and 15% of all parotid gland tumors. However, they seem to occur most often in the minor, rather than major, salivary glands. The disease is unique in that its tumors grow slowly, but metastasize readily.
Clinical evaluation of a potential salivary gland mass typically includes a physical examination, a CT scan and/or an MRI, followed by surgical excision of the abnormality.