Salivary Gland Tumors: An Overview for Providers

Salivary gland tumors are rare, making up only 6 to 8 percent of head and neck tumors¹. Most are noncancerous. However, salivary gland carcinomas, particularly within the parotid gland, and rates of regional metastases are on the rise². The majority of benign tumors are seen in people under the age of 50, while salivary gland cancers (SGC) tend to be seen in the sixth decade of life.

Salivary glands line parts of the nose, mouth, oropharynx and larynx. The largest of these are the parotid and submandibular glands, with the parotid gland being the most frequent site of tumor incidence (80-85%). Of parotid gland tumors, the majority are benign, while about 25 percent are malignant. Generally, the smaller the salivary gland, the lower the incidence rate but the higher the likelihood of malignancy; 40 to 45 percent of submandibular gland tumors, 70 to 90 percent of sublingual gland tumors, and 50 to 75 percent of minor salivary tumors are cancerous. 

Distinguishing the benign from the malignant typically requires an evaluation by an otolaryngologist, head and neck surgeon, but often patients will present first to primary care, the emergency department, and in some cases, their dentists. “Anyone who has a neck mass, not just in the salivary glands, and doesn’t have any associated infection symptoms, such as pain, fever or purulence and that last more than two weeks, should be seen by an otolaryngologist or oral surgeon,“ says Alexandra Kejner, M.D., FACS. Dr. Kejner is an Associate Professor of Otolaryngology, Head and Neck Surgery at MUSC Health. Specifically, she specializes in head and neck oncology and microvascular reconstructive surgery. 

Initial examination 

Salivary gland tumors may present as a painless mass in the face or neck, mouth or the back of the throat. More advanced findings include numbness or facial palsy on one side. A key element of examining these patients is the inclusion of a cranial nerve exam with a particular focus on facial and periauricular numbness, muscles of facial expression, palatal elevation and tongue movement. 

Examining these patients should involve visual examination as well as bimanual palpation. The parotid gland can best be examined by facing the patient and evaluating symmetry, sensation, facial movement and then bimanually palpating the parotid from within the mouth as well as externally. For the submandibular gland, a similar approach should be undertaken. 

Using two hands, the provider should press on the outside just under the jawbone while palpating from the inside of the mouth to feel for any abnormalities. “Salivary glands should feel soft and non-tender,” Dr. Kejner says. If a salivary gland is firm or painful or different from the other side, the patient should be referred to a specialist for further investigation. 

Dr. Kejner also recommends examining the inside of the mouth, which should be fairly uniform in color. White or red spots or bumps/asymmetries inside the mouth or throat that do not resolve or change within two weeks should be referred to a specialist. Masses can arise within the deep lobe of the parotid in the parapharyngeal space, and these can appear similar to a peritonsillar abscess or a lump adjacent to the tonsil. Masses in this area can be malignant or benign but require further imaging and work-up. 

Types of tumors 

The World Health Organization lists head and neck tumors.

The most common tumors, from most common to least, are: 

● Pleomorphic adenoma
● Warthin tumor
● Mucoepidermoid carcinoma
● Adenoid cystic carcinoma
● Acinic Cell carcinomas
● Salivary ductal carcinoma 

While the etiology of many salivary gland tumors is unknown, there are some factors that have been associated with increased risk: history of prior radiation (high dose or radiation exposure from nuclear testing), smoking, some viral infections and environmental factors, including exposure to rubber manufacturing, hair dressings and high levels of nickel. 

Diagnosis and Treatment 

Most tumors will require imaging and biopsy to arrive at a definitive diagnosis of benign or malignant. Imaging may involve ultrasound, computed tomography (CT), or magnetic resonance imaging (MRI). Biopsy can be accomplished either by fine needle aspiration (where a 25-gauge needle is used to sample cells from the tumor) or by a core biopsy (which is a slightly larger bore needle that takes a sample similar to a soil sample). Depending on diagnosis, treatment options can be offered. Typically for salivary glands, the first line of treatment is surgery. 

Different levels of surgery depend on the type and stage of the tumor, the degree to which it has affected surrounding tissue (e.g., lymph nodes) and its location. For benign tumors, typically most of the salivary gland can be preserved. For malignant tumors, typically the tumor will be removed with additional margins. Sometimes, this means removing the entire gland. For higher-grade tumors, including mucoepidermoid carcinoma and salivary ductal carcinoma, lymph node removal (neck dissection) may also be indicated. During surgery, the surgeon may use something called a nerve integrity monitoring system, which helps detect ultrafine movement around the nerves and decreases the incidence of postoperative facial weakness. 

For benign tumors, the risk to cranial nerves is typically low; however, for malignant tumors sometimes resection may involve sacrifice of the facial nerve, which can be incredibly distressing. New techniques of reconstruction now allow for immediate reconstruction of nerve structures. In addition, there are postoperative methods of improving facial function. 

After surgery is complete, for benign and low-grade tumors the risk of recurrence is relatively low. For high-grade or metastatic lesions, further therapy is often indicated, and this typically involves radiation. In some cases, the tumor tissue may be sent to the lab to assess for tumor markers or androgen receptors. If positive, hormonal therapies can sometimes be used as another adjunct in treatment. 

Research is currently underway regarding optimal treatment of salivary gland malignancies. Visit the American Head and Neck Society for more information. 

References 

1. Del Signore AG, Megwalu UC. The rising incidence of major salivary gland cancer in the United States. Ear Nose Throat J 2017;96(3):E13–6.
2. El-Naggar AK, Chan JKC, Grandis JR, et al. World Health Organization Classification of Tumours of Head and Neck, IARC, Lyon 2017.