Most patients with benign tumors of the major or minor salivary glands present with painless swelling of the parotid, submandibular, or the sublingual glands. Neurological signs, such as numbness or weakness caused by nerve involvement, typically indicate a malignancy. Facial nerve weakness that is associated with a parotid or submandibular tumor is an ominous sign. Persistent facial pain is highly suggestive of malignancy; approximately 10% to 15% of malignant parotid neoplasms present with pain.[8,14] (Refer to the PDQ summary on Pain for more information.) The majority of parotid tumors, both benign and malignant, however, present as an asymptomatic mass in the gland.[2,8]
Early-stage low-grade malignant salivary gland tumors are usually curable by adequate surgical resection alone. The prognosis is more favorable when the tumor is in a major salivary gland; the parotid gland is most favorable, then the submandibular gland; the least favorable primary sites are the sublingual and minor salivary glands. Large bulky tumors or high-grade tumors carry a poorer prognosis and may best be treated by surgical resection combined with postoperative radiation therapy. The prognosis also depends on the following:[16,17]
- Gland in which they arise.
- Grade (i.e., degree of malignancy).
- Extent of primary tumor (i.e., the stage).
- Whether the tumor involves the facial nerve, has fixation to the skin or deep structures, or has spread to lymph nodes or distant sites.
Overall, clinical stage, particularly tumor size, may be the crucial factor to determine the outcome of salivary gland cancer and may be more important than histologic grade.
Perineural invasion can also occur, particularly in high-grade adenoid cystic carcinoma, and should be specifically identified and treated. Radiation therapy may increase the chance of local control and increase the survival of patients when adequate margins cannot be achieved.[Level of evidence: 3iiiDii] Unresectable or recurrent tumors may respond to chemotherapy.[21,22,23] Fast neutron-beam radiation therapy or accelerated hyperfractionated photon-beam schedules have been shown to be effective in the treatment of inoperable, unresectable, and recurrent tumors.[24,25,26]