Parotid & Other Salivary Gland Tumors
What are salivary glands?
As one might expect, the salivary glands are responsible for secreting saliva into the mouth to moisten the oral cavity and assist in breaking down food. Humans have three pairs of major salivary glands. These consist of the parotid glands, submandibular glands, and sublingual glands. The parotid glands are located anterior to the ear, over the angle of the jaw and extending into the upper neck. The submandibular glands are smaller and are located under the jaw. The sublingual glands are the smallest major salivary glands and are located anterior to the submandibular glands, also under the jaw. In addition to the major salivary glands, hundreds of minor salivary glands, each about the size of a grain of sand, line the membranes of the inside of the mouth.
What are salivary gland tumors?
Tumors can arise from the various cells in the salivary glands when the body’s normal regulating mechanisms do not function the way they are supposed to. Salivary gland tumors can be either benign (non-cancerous) or malignant (cancerous). Tobacco use is a risk factor for the development of malignant salivary gland tumors. As a general rule, the likelihood of a salivary gland tumor being malignant is inversely proportional to the size of the gland. Tumors of the parotid glands, the largest salivary glands, have only a 20% likelihood of malignancy, whereas tumors of the minor salivary glands have an 80% likelihood of being malignant. The most common type of benign salivary gland tumor is a benign mixed tumor, or pleomorphic adenoma. The next most common benign tumor is a Warthin’s tumor, which is found only in the parotid gland, and which can sometimes occur bilaterally. The most common types of malignant tumors of the salivary glands are mucoepidermoid carcinoma, adenoid cystic carcinoma, adenocarcinoma, carcinoma ex pleomorphic adenoma, and acinic cell carcinoma.
How are salivary gland tumors diagnosed?
Most salivary gland tumors are noticed by the patient as a lump in the face or neck. There are rarely any other symptoms. Pain is uncommon. Weakness of the muscles of the face on the side of the tumor is a worrisome finding. Once a salivary gland tumor has been detected, further diagnostic testing, such as a CT or MRI scan, may be recommended. A fine needle aspiration (FNA) biopsy of the tumor may also be recommended to try to determine the type of tumor. It is important to realize that needle biopsies are not 100% accurate. Results of these biopsies should be thought of as a guide, but not an absolute indication as to whether the tumor is benign or malignant.
How are salivary gland tumors treated?
Surgical excision is the treatment of choice for most salivary gland tumors. Even tumors felt to be benign on needle biopsy should generally be removed, since the biopsy may be inaccurate and the tumor will typically continue to grow, leading to increasing cosmetic and functional problems, and potentially more difficult surgery in the future. Exceptions to this recommendation include situations in which a tumor is felt to be benign and the physical condition of the patient makes him or her a poor candidate for surgery. Surgery to remove the parotid gland is called a parotidectomy. Surgeries to remove the submandibular gland or sublingual gland are referred to as excision of submandibular gland, and excision of sublingual gland, respectively. If the tumor is malignant, the physician may recommend additional treatment, including dissection of lymph nodes in the neck beneath the gland (neck dissection), or radiation therapy.
By Cary Moorhead, MD
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