Minor Salivary Gland Cancer

Minor salivary gland tumors are a type of head and neck tumor. These tumors include benign and malignant tumors (minor salivary gland cancer). Most minor salivary gland tumors are malignant. The most common minor salivary gland tumor is usually either mucoepidermoid carcinoma or adenoid cystic carcinoma. Minor salivary gland carcinomas are malignant tumors. Pleomorphic adenoma of the minor salivary gland is the most common benign tumor of the minor glands.

Minor salivary gland tumors of the palate (roof of the mouth) are most common. The reasons for the occurrence of minor salivary gland tumors are uncertain. Tobacco use, radiation exposure, exposure to chemicals, and alcohol consumption are some of the risk factors for the development of minor salivary gland tumors. Signs and symptoms of malignant minor salivary gland tumors may vary according to their location. Avoiding risk factors may be beneficial in minor salivary gland tumor prevention.

The diagnosis of a minor salivary gland tumor is possible with a biopsy. Survival rate may vary depending on the type of minor salivary gland tumor, location, spread, age, and general health of the patient. Surgery is the main treatment for tumors of minor salivary glands. When necessary, radiation therapy and sometimes chemotherapy also take part in the treatment.

Minor Salivary Glands

Humans have 3 pairs of major salivary glands (parotid, submandibular, and sublingual) and hundreds of minor salivary glands. Minor salivary glands are interspersed on the surface (mucosa) of areas such as the lips, oral cavity, throat, nasal cavity, and sinuses. Minor salivary glands in the mouth and throat continuously produce and secrete saliva to keep the mucosa moist.

In general, as the size of the salivary gland decreases, the risk of malignancy of the salivary gland tumor increases. Most parotid tumors and half of the submandibular gland tumors are benign. Most of the sublingual gland tumors are malignant. Minor salivary glands are much smaller structures than these glands, and their tumors are usually malignant.

Signs and Symptoms of Minor Salivary Gland Cancer

Benign minor salivary gland tumors are mostly slow-growing (over months and years) tumors of areas such as the palate, lips, tongue, inner cheek, gum, and the floor of the mouth. However, benign minor salivary gland tumors can also turn into malignant tumors over time. Malignant minor salivary gland tumors usually develop and grow in a shorter period of time (weeks or months).

Minor salivary gland tumors of the palate are most common due to the high concentration of salivary glands in this region. In terms of the incidence of the tumor, the lips, inner cheek mucosa, tongue, and floor of mouth follow the roof of the mouth.

It is necessary to distinguish palatal abscesses, cysts, and other soft tissue tumors from minor salivary gland tumors of the palate. Abscesses can be excluded because of lots of signs and symptoms of inflammation.

Swelling in the mouth or throat

The minor salivary gland tumor presents itself as swelling, lump, or growth of the mucosa that usually exists for more than 2-3 weeks. Swelling is the most common sign of minor salivary gland tumors. In particular, swelling in the palatal region resembles a dental abscess and cyst, so it is necessary to be careful in such swelling.

Pain in the mouth or throat

A minor salivary gland tumor, whether it is benign or malignant, can cause difficulty speaking and pain. These symptoms depend on the size and spread of the tumor rather than whether the minor salivary gland tumor is benign or malignant. However, the presence of pain is more common for malignant tumors.

Ulceration in the mouth or throat

Minor salivary gland tumors, whether they are benign or malignant, rarely cause ulceration. They present themselves as swelling rather than ulcers in the oral mucosa. However, the presence of overlying mucosal changes and ulceration is more common for malignant tumors.

Swollen lymph nodes in the neck

Malignant minor salivary gland tumors are less likely to spread to lymph nodes in the neck compared to other salivary gland tumors. If there are metastases to the neck lymph nodes, swelling may occur on the side(s) of the neck.

No symptoms

Tumors of minor salivary glands may not show any symptoms at first, depending on the area where they develop and the stage of the tumor. For example, they show symptoms in the nasal cavity and sinuses in the late stages. Sometimes, head and neck imaging tests are taken for other reasons find them by chance.

Causes

Although tobacco use, exposure to radiation, exposure to chemicals for occupational reasons, and alcohol consumption are blamed for the development of malignant minor salivary gland tumors, there is no scientifically clear evidence. The effect of viruses, diet, or other factors on tumor development is also unclear. The reasons for the formation of benign minor salivary gland tumors are more uncertain.

Risk Factors

The distribution of minor salivary gland tumors is almost equal for both sexes. Most of the cases occur in the 5-6th decades. Minor salivary gland tumors can develop at any age, including childhood. However, benign minor salivary gland tumors are common in the young age group, and malignant tumors in older people.

Being older

Although the tumors of minor salivary glands can occur at any age, malignant tumors are most common in late middle age and older adults.

Tobacco use

Tobacco use is a very important risk factor in many head and neck cancers. The smoke of tobacco particularly affects the oral cavity and throat mucosa. In this respect, especially malignant minor salivary gland tumors in these regions may be associated with smoking. Because tobacco use is common in patients.

Exposure to radiation

Exposure to radiation (including radiation therapy) is a risk factor for minor salivary gland tumors. Some doubts today also focus on the electromagnetic effect emitted by mobile phones.

Exposure to chemicals

People who work with certain chemicals may have an increased risk of minor salivary gland tumors due to regular exposures. The chemical industry, mining, plumbing, rubber, or nickel industries are among the risky jobs in this respect.

Alcohol consumption

Unlike other head and neck tumors associated with alcohol consumption, the role of alcohol in most salivary gland tumors is often unclear. The effect of alcohol consumption on minor salivary gland tumor development has not yet been confirmed.

Types of Tumors

A tumor refers to the masses formed by the uncontrolled proliferation of cells. Tumors can develop from any tissue in the body, as well as from salivary glands. Generally, tumors can be benign or malignant. Minor salivary gland tumors are usually malignant. We call the malignant tumors of the minor salivary glands as minor salivary gland cancer.

Benign minor salivary gland tumors

Benign tumors of the minor salivary glands grow slowly. They generally do not spread to surrounding tissues and organs in distant regions. They grow by pushing the surrounding tissues and making room for themselves, without invading the surrounding tissues with extensions. This growth occurs over months, even years. The most common benign minor salivary gland tumors are the following;

Pleomorphic adenoma (benign mixed tumor)

Pleomorphic adenoma of the minor salivary gland is the second most common tumor among all tumors of minor glands. Also, most of the benign tumors of the minor salivary glands are pleomorphic adenomas. Pleomorphic adenoma is most common in the parotid gland, but can also develop from minor salivary glands of areas such as the mouth and throat.

If pleomorphic adenoma of the minor salivary gland remains untreated, or if it is not completely removed, it can turn into a malignant tumor over the years. In this case, the growth of the slowly growing tumor that has existed for years is accelerated. Scientific studies have shown that one-tenth of pleomorphic adenomas that have existed for more than fifteen years can become cancerous.

Basal cell adenoma

Basal cell adenoma is a benign tumor that mostly originates from the parotid gland. However, basal cell adenoma can also develop from minor salivary glands.

Oncocytoma

Oncocytoma is a benign tumor that mostly originates from the parotid gland. However, sometimes oncocytoma can also develop from minor salivary glands. This tumor originates from a type of salivary gland cell called an oncocyte.

Other benign tumors

Although rare, benign tumors such as canalicular adenoma, myoepithelioma, and monomorphic adenoma may develop from minor salivary glands. Apart from this, it is possible to see masses of the minor salivary gland originating from vessels such as hemangioma, lymphangioma (cystic hygroma), and salivary gland cysts.

Malignant minor salivary gland tumors

Minor salivary gland cancers grow rapidly. These tumors have the potential to metastasize to the lungs, liver, brain, bone, and other distant regions. They invade surrounding tissues (muscle, cartilage, bone, nerve, and others) and develop by disrupting their functions. Relatively minor salivary gland tumors with a low malignancy potential are seen in childhood and young adults. The common malignant tumors are minor salivary gland carcinomas. The most common malignant minor salivary gland tumors are the following;

Adenoid cystic carcinoma

Adenoid cystic carcinoma is one of the two most common minor salivary gland carcinomas. This tumor penetrates the nerve fibers in its area and uses them as a way to spread. Adenoid cystic carcinoma spreads through the blood rather than lymph. It tends to recur many years after treatment (usually surgery and radiation therapy) and lung metastases are common. Adenoid cystic carcinoma is more common in people of middle age and older.

Mucoepidermoid carcinoma

Mucoepidermoid carcinoma is another of the two most common minor salivary gland carcinomas. Generally, relatively slow-growing types with a low malignancy potential are seen. However, there may be fast-growing types with a low malignancy potential and poor prognosis. The patients are usually middle-aged and older adults, but there may be younger patients also.

Adenocarcinoma

Polymorphous adenocarcinomas are one of the most common adenocarcinomas in minor salivary glands. Polymorphous adenocarcinomas are usually slow-growing cancers. Some types of adenocarcinomas tend to have low malignancy potential (eg acinic cell carcinoma) and generally have a good prognosis. However, types such as oncocytic carcinoma and salivary duct carcinoma are more likely to behave with a high malignancy potential and have a less positive outlook.

Acinic cell carcinoma

Acinic cell carcinoma, a type of adenocarcinoma, accounts for about one-tenth of malignant salivary gland tumors. It often develops from the parotid gland. Acinic cell carcinoma is a malignant tumor with a low malignancy potential. It grows slowly and is less likely to spread to distant organs.

Acinic cell carcinomas are more common in women than men. Apart from this, acinic cell carcinoma can also be seen in children and older people. Acinic cell carcinoma, which is mostly a tumor of young adults, has a better prognosis compared to other minor salivary gland cancers.

Malignant mixed tumors

The malignant mixed tumor is a less common type of malignant salivary gland tumor which specific to older ages. Carcinoma ex pleomorphic adenoma is the most common type of these. This tumor occurs when a pleomorphic adenoma of the minor salivary gland has not been treated for many years and transforms into a malignant tumor. In this case, the tumor that has existed for years in the mouth, throat, nasal cavity, and sinus suddenly begins to grow rapidly. Carcinoma ex pleomorphic adenoma is a highly aggressive tumor. It has very low cure rates regardless of treatment.

Other malignant tumors

Although rare, squamous cell carcinoma, non-Hodgkin lymphoma, and other cancers may develop from salivary glands. Squamous cell carcinoma occurs mainly in older men. It may develop after radiation therapy in the area and tends to have a poorer outlook.

Non-Hodgkin lymphoma can rarely begin in the immune system cells in the minor salivary glands. Non-Hodgkin lymphomas that start in the salivary glands affect people with Sjögren’s syndrome.

Diagnosis for Minor Salivary Gland Cancer

A patient who suspects salivary gland cancer of the mouth or throat should first consult an ear, nose, and throat doctor (otolaryngologist). The diagnosis begins when the patient, who notices the swelling or mass of the areas such as the mouth and throat, consults a doctor. The doctor listens to the patient’s complaints and asks various questions to the patient. Then the doctor proceeds to the examination phase.

Physical exam

Generally, an otolaryngologist performs a thorough examination of the patient’s ear, nose, mouth, throat, and neck. The doctor carefully examines the minor salivary gland tumor for size and extension. Later, the doctor examines the mouth and throat where the minor salivary gland tumor develops with a special device called an endoscope. The doctor checks for growth in the lymph nodes in the neck.

Removing a tissue sample

Taking cell or tissue samples from a minor salivary gland tumor is necessary to confirm the diagnosis. If the minor salivary gland tumor is in the mouth or throat mucosa, the diagnosis is made by taking tissue samples from the tumor in the mouth or throat. If the tumor is in the form of a lump under the skin and the mass does not have a relationship with the oral cavity, it is safer to take tissue samples with a fine needle biopsy.

Tumors of minor salivary glands usually develop in areas covered by the mucosa, such as the inside of the mouth and throat. In this case, the doctor takes the tissue samples by incision with surgical instruments under local anesthesia. This process does not lead to the spread of the tumor.

The pathologist reports the diagnosis to the doctor after examining the cell and tissue samples taken from the minor salivary gland tumor. The pathologist report guides the surgeon in the planning of the treatment.

Sometimes the surgeon may skip the preoperative biopsy stage, which gives a lot of information about the type of minor salivary gland tumor. Instead, the surgeon surgically removes the entire tumor. Then the pathologist examines the removed tumor in detail and reaches the final diagnosis. However, the preoperative biopsy is still likely to provide important information.

Imaging tests

The doctor who suspects a minor salivary gland tumor may require tests such as ultrasonography (USG), magnetic resonance imaging (MRI), or computed tomography (CT).

MRI imaging provides more information about soft tissues and their properties. Accordingly, an MRI imaging taken with intravenous medication (contrast agent) is a common examination to examine the salivary gland tumor. The radiologist interprets the image of the mass in imaging tests and reports it to the doctor.

Imaging tests help diagnose minor salivary gland tumors. Benign minor salivary gland tumors are well-circumscribed on MRI or CT, and they do not appear to invade surrounding tissues. However, malignant tumors of the minor salivary glands often invade the surrounding tissues depending on their location and have an unclear border.

In cases where adenoid cystic carcinoma is diagnosed in the minor salivary gland, it becomes important to investigate metastases. Because there is a risk of this tumor spreading to distant organs such as the lungs. In these cases, examinations such as positron emission tomography (PET) and lung CT are important.

Minor Salivary Gland Cancer Treatment

Regardless of benign or malignant, the main treatment for all minor salivary gland tumors is the surgical removal of the tumor. One of the main reasons for this is that benign tumors of the minor salivary glands will continue to grow over time. In this case, their treatment will be more difficult. Another reason is the possibility that benign tumors of the minor salivary glands can turn into minor salivary gland cancer over time. In addition, there are transitional zone tumors of the minor salivary gland that are not known to be benign or malignant.

If the minor salivary gland tumor is completely removed and the tumor is a benign tumor according to the pathological examination, there is no need for additional treatments. Radiation therapy and chemotherapy do not have many places in the treatment of benign tumors of the minor salivary gland.

After the removal of the minor salivary gland cancer, the patient receives additional treatments such as radiation therapy and sometimes chemotherapy. However, if the general health condition of the patient is not suitable for surgery or if the minor salivary gland tumor has spread that does not allow surgical removal, other treatments may come into prominence.

Treating doctors

Disorders in the mouth and throat area related to minor salivary glands mainly concern otolaryngologists. In general, otolaryngologists experienced in head and neck surgery perform surgical removal of minor salivary gland tumors. Radiologists, radiation oncologists, medical oncologists, plastic surgeons, dentists, and psychologists can also participate in the diagnosis and treatment of the tumor.

Surgery

Minor salivary gland tumor surgery is performed under general anesthesia. These tumors can develop from the palate, tongue, lips, inner cheek, the floor of the mouth, larynx, pharynx, nasal cavity, sinuses, neck, and various other regions. Therefore, tumor removal surgery may vary depending on the location of the tumor.

Tumor removal

The surgeon completely removes the minor salivary gland tumor with some healthy tissue around it. Removal of the tumor is performed by an incision in the mouth or on the neck, depending on the location, size, or spread of the tumor to the surrounding tissues. In particular, tumors in the nasal cavity and sinuses are usually at a later stage when diagnosed. Accordingly, the surgeon removes more surrounding tissues along with the tumor in these cases.

Lymph node removal

During tumor removal surgery, neck lymph nodes that may contain metastasis are also removed (neck dissection). Neck dissection has become a standard procedure in the treatment of many malignant tumors located in the face, mouth, throat, head, and neck regions.

During neck dissection, neck lymph nodes, where the minor salivary gland cancer has the highest probability of spreading, are removed. However, due to the low metastasis rate of many malignant minor salivary gland tumors to the neck lymph nodes, optional neck dissection is not required.

The surgeon usually performs the neck dissection during the removal of the minor salivary gland cancer. If the diagnosis of cancer is made in post-surgical pathological examinations, the surgeon performs a second surgery for neck dissection. Neck dissection has no place in the treatment of benign tumors of the minor salivary glands.

Reconstruction

After removing the minor salivary gland tumor, the surgeon goes into the repair phase. The surgeon may have removed muscle, cartilage, nerve, or bone tissue from the area due to the spread of the tumor. If the surrounding tissues are not sufficient for repair, the surgeon may need the transfer of muscle, cartilage, or bone tissues from other parts of the body to repair the mouth, throat, or jaw.

Normalization after surgery

After minor salivary gland tumor surgery, the patient stays in the hospital for a while. Depending on the region and size of the surgery, the patient may spend a few days in intensive care during this period. To remove blood and fluid accumulation from the surgical wound, the patient carries the drains placed in the surgical area for a while.

In the postoperative period, the patient may have pain. That’s why the patient takes pain relievers for a few days. The patient also takes antibiotics against infections. Because infections can sometimes be seen after surgeries.

After surgery, the patient’s face and neck may swell as a result of blood and fluid accumulation. This situation often passes without causing any problems. Pain and swelling may occur due to bandages. These will pass as the patient gets rid of the bandages.

Radiation therapy

Radiation oncologists deliver radiation therapy. Radiotherapy is the delivery of radiation by special devices to the tumor area and the areas where the tumor is likely to spread. Radiation therapy is usually for malignant tumors of the minor salivary glands. In very rare cases, some persistent benign tumors of the minor salivary glands may also require radiation therapy.

Although the main treatment for minor salivary gland cancers is surgery, radiation therapy also takes part in the treatment because it increases the effect of the surgical treatment. Radiation therapy increases the patient’s chance of getting rid of cancer. Radiation therapy is usually an additional post-surgery treatment. Normally, radiation therapy is not used as the sole treatment for minor salivary gland tumors.

Chemotherapy

Medical oncologists apply chemotherapy. Chemotherapy uses anti-cancer drugs which kill cancer cells in the body. Chemotherapy is not the standard treatment for malignant tumors of the salivary glands. The drug is useless if there is no inflammation-like condition of the salivary gland.

For salivary gland cancers, the benefit of chemotherapy is limited. Chemotherapy has a place mainly in the treatment of salivary gland lymphomas. Apart from this, chemotherapy may be needed in the presence of metastasis or in salivary gland cancers where the complete removal of the tumor is not possible.

Targeted therapy

No targeted therapy drugs have so far been effective in salivary gland cancers. Targeted therapy research for the treatment of salivary gland cancers is still at an early stage.

Salivary functions after surgery

There are 3 pairs of major and hundreds of minor salivary glands that secrete saliva into the mouth through various ducts. In this respect, removing one or more of the minor salivary glands due to the tumor does not cause a decrease in the amount of saliva. Other salivary glands take over the function of the missing gland without any problem. However, the patient who received radiation therapy after surgery will have a decrease in saliva (dry mouth) for a while due to the side effects of radiation. For the patients, mouth moisturizers with the American Dental Association (ADA) seal (eg, Biotene Dry Mouth Oral Rinse, or as a different choice: TheraBreath Dry Mouth Oral Rinse, etc.) may be beneficial.

Speaking and feeding after surgery

After minor salivary gland tumor surgery, the patient is not given food or liquid orally until the effect of anesthesia disappears. Depending on the size of the surgery, the patient feeds for a while through a vein or a tube extending into the stomach. The patient starts to eat soft foods over time and then switches to normal foods.

It may take time for the patient to switch to a normal diet, especially after extensive surgeries performed for large tumors of the minor salivary glands. Unless the palate, tongue, lips, throat, pharynx, or jawbone are removed due to the tumor, functions such as feeding and speaking are not permanently affected.

Saliva helps digestion by keeping the mouth and throat moist. In addition, saliva creates a defense mechanism against microorganisms that cause infections in the mouth and throat. Since radiation therapy causes a decrease in saliva secretion, saliva cannot fully perform its functions. Therefore, after radiation therapy, wounds may occur in the patient’s skin, mouth, and throat areas. Although these problems pass over time, the patient may experience difficulties in speaking and feeding for a while.

Prognosis

Prognostic factors for survival in minor salivary gland cancer mostly depend on the type of tumor, the stage of cancer, the location of the tumor, the age of the patient, and the presence of distant metastases. Overall, the prognosis for salivary gland cancers is better in children and adolescents. This is due to the lower frequency of metastases, less local tissue spread, and different types of cancer. The overall survival rate for children after surgical treatment is better than for adults.

In minor salivary gland cancers, the most common locations for the metastasis include; the lungs, bone, liver, and brain. Distant metastases are the main cause of death in minor salivary gland cancer. In this respect, if minor salivary gland cancer is found early and treated, the prognosis is good.

Follow-up care

One of the main goals of regular doctor check-ups after cancer treatment is to detect recurrence. The other goal is to manage any treatment complications that may arise. Long-term follow-up is very important for minor salivary gland tumors.

Most recurrences in minor salivary gland cancers occur in the first 3 years after treatment, except for tumors with a low malignancy potential and adenoid cystic carcinomas. Patients should receive regular follow-up at certain intervals within 5 years after treatment. After the 5th year, the patient should receive regular follow-up every 1 year.

Salivary gland cancers require observation for up to 20 years after treatment. Particular attention should be paid to adenoid cystic carcinoma due to delayed recurrence or tendency to metastasis. Annual chest imaging is important for tumors with a high malignancy potential because of the high risk of pulmonary metastasis. Patients who receive radiation to the neck area should have their thyroid hormone levels checked several times a year.

Recurrence of tumor

Approximately half of all malignant salivary gland tumors recur after initial treatment. Minor salivary gland tumors can recur after treatment. In these cases, the surgeon removes the tumor completely, along with the surrounding tissues, with repeat surgery, if possible. These surgeries are more difficult than the first one. Because minor salivary glands can be in various places that are difficult to reach surgically. Apart from this, it will not be easy to recognize and protect important structures (especially nerves) in the region due to the healing tissues formed after the previous surgery.

Prevention

The cause of minor salivary gland tumors is unknown. In particular, there is less information available regarding the causes of benign tumors. As the cause is unknown, ways to avoid minor salivary gland tumors are also unclear. However, it may be helpful to avoid certain behaviors to reduce the risk of developing minor salivary gland cancer.

Quit smoking

Tobacco use may affect the formation of minor salivary gland tumors in terms of exposing the mouth and throat to some carcinogenic substances. Especially if the person is older, this risk will increase even more. In general, this opinion prevails that avoiding smoking can reduce the risk of minor salivary gland tumors.

Reduce radiation exposure

Even if it is for therapeutic purposes, radiation taken to the head and neck regions (especially during previous radiation treatments or dental treatments) is shown as the cause of minor salivary gland tumors. This risk is even greater if the person is older. Avoiding unnecessary radiation to the head and neck area can reduce the risk of minor salivary gland tumors. Using a mobile phone as little as possible or using a headset without bringing the phone close to the head and neck area while talking may also reduce the risk.

Reduce chemical exposure

People who work with risky chemical substances due to their profession should work in a protected environment as much as possible. These people mostly work in jobs related to the chemical industry, mining, plumbing, rubber, or nickel industries.

Reduce alcohol consumption

Alcohol consumption affects the occurrence of some mouth and throat cancers. However, there is no evidence yet for the effect of alcohol on minor salivary gland tumor development. To reduce the risk, it may be helpful to reduce alcohol consumption. Also, the use of alcohol-containing oral care products is as risky as alcohol consumption. Because they regularly and continuously expose the mouth to alcohol. So, the use of alcohol-free products (for example, oral rinses with the American Dental Association (ADA) seal such as TheraBreath Fresh Breath, CloSYS Sensitive Gentle Mint, CloSYS Ultra Sensitive Unflavored, or a different choice: Tom’s of Maine Natural Wicked Fresh Mouthwash, etc.) is safer.

Get a regular dental check-up

Routine dental examinations detect many minor salivary gland cancers first. Regular examination of the dentist is important to detect minor salivary gland cancer at an earlier stage.

Live a healthy life

A healthy diet, strong immunity, and high morale are important to reduce the risk of developing all types of cancer, including minor salivary gland cancer. A diet rich in vitamin C and low in cholesterol can be effective in preventing salivary gland cancer.