Adenoid Cystic Carcinoma of Salivary Gland

Adenoid cystic carcinoma of the salivary gland is a rare and slow-growing cancer that can be challenging to diagnose and treat. While it has a good survival rate in the first five years, this cancer has a strong tendency to return even many years after treatment, making long-term monitoring essential.

Table of contents

• What is adenoid cystic carcinoma of the salivary gland?
• How common is this cancer?
• Signs and symptoms
• What causes this cancer?
• How the cancer spreads
• How is it diagnosed?
• Treatment options
• Outlook and survival
• The importance of long-term monitoring

What is adenoid cystic carcinoma of the salivary gland?

Adenoid cystic carcinoma (ACC) is an uncommon type of cancer that usually develops in the salivary glands (glands that make saliva to keep your mouth moist). These glands are located in different areas of your head and neck^[1].

You have three major salivary glands on each side of your face. The parotid glands are located near your ears. The submandibular glands sit below your jawbone, and the sublingual glands are tucked under your tongue^[4]. Besides these major glands, you also have many smaller salivary glands throughout your mouth, throat, and nose area^[2].

ACC tumors can look different under a microscope. They might be solid and round, or they might have holes in them that make them look like Swiss cheese^[1]. While ACC most commonly affects the salivary glands, it can also develop in other parts of the body where secretory glands are found, such as the breast, tear glands, sweat glands, or reproductive organs^[2].

One of the most important features of ACC is that it grows slowly compared to other cancers. However, this slow growth can be deceptive. The cancer can become aggressive and unpredictable over time, and it has a strong tendency to come back even after successful treatment^[1].

• Salivary glands (parotid, submandibular, sublingual)
• Minor salivary glands throughout mouth and throat
• Lacrimal glands (tear glands)
• Sweat glands
• Other secretory glands throughout the body

How common is this cancer?

Adenoid cystic carcinoma is a rare disease. It makes up about 1% of all cancers that develop in the head and neck region^[1]. In the general population, it affects approximately 4.5 out of every 100,000 people^[2]. In the United States, roughly 1,200 people receive this diagnosis each year^[1].

Despite being rare overall, ACC is actually one of the most common types of cancer that affects the salivary glands. It accounts for about 10% of all salivary gland tumors, making it the second most common malignant tumor (cancerous growth) of the major salivary glands^[2]. For the minor salivary glands, ACC is the most common type of cancer^[2].

Most people who develop ACC are between the ages of 40 and 60, though it can occur at any age^[1]. The disease affects women slightly more often than men, with about 60% of cases occurring in women and 40% in men^[2].

Signs and symptoms

Because adenoid cystic carcinoma grows slowly, it may not cause any symptoms in the early stages^[1]. This makes early detection difficult. When symptoms do appear, they depend on the size and location of the tumor^[1].

The most common first sign is a painless lump. This lump might appear inside your mouth, often under your tongue or inside your cheek. You might also notice a lump below your jaw or near your ear^[4].

Other symptoms you might experience include^[1]:

• Difficulty breathing through your nose or nasal congestion (blocked nose)
• Nosebleeds
• Difficulty swallowing
• Hoarseness (a rough or raspy voice)
• Muscle weakness in your face
• Vision changes
• Pain or numbness in your face

One distinctive feature of ACC is that the cancer can spread along nerve fibers. This means you might experience facial pain or numbness even if the tumor itself is small or located elsewhere^[4].

If you notice any of these symptoms, especially a lump that persists or grows, you should talk to your doctor. While these symptoms can be caused by many conditions that are not cancer, it’s important to get them checked^[4].

What causes this cancer?

Doctors and scientists don’t fully understand what causes adenoid cystic carcinoma. The cancer appears to develop because of genetic mutations (changes in genes) that happen during a person’s lifetime, rather than being inherited from parents^[1].

Unlike many other head and neck cancers, ACC is not linked to smoking or alcohol use^[2]. In fact, there are no known risk factors that make someone more likely to develop this cancer. It doesn’t run in families, and researchers haven’t identified any environmental or lifestyle factors that increase risk^[1].

Recent research has uncovered some important genetic features of ACC. Scientists have found that most cases involve activation of a gene called MYB. This gene becomes overactive through different mechanisms, such as genetic fusion with another gene called NFIB. In some cases, a related gene called MYBL1 is involved instead^[6]. These genetic changes appear to drive the development and growth of ACC tumors.

How the cancer spreads

Adenoid cystic carcinoma has two main ways of spreading to other parts of the body^[1]:

The first is called perineural invasion. This means the cancer cells creep along the nerve fibers that surround the tumor. This type of spread is very common in ACC and happens on such a tiny, microscopic level that it can be hard for doctors to detect on imaging scans or even during surgery^[1]. This is one reason why ACC often comes back after treatment.

The second way is through the bloodstream. Cancer cells can break away from the main tumor and travel through your blood to other organs^[1]. When ACC spreads to distant parts of the body (called metastatic or Stage 4 disease), it most commonly affects the lungs and liver^[1].

Unlike many other types of cancer, ACC doesn’t usually spread to lymph nodes (small bean-shaped structures that help fight infection). However, it does happen in about 5% to 10% of cases^[1].

How is it diagnosed?

If your doctor suspects you might have adenoid cystic carcinoma, they will start by examining your mouth, face, and neck. They will check for lumps, look at how your face moves, and feel for any swollen lymph nodes. They’ll also ask about your symptoms, such as pain, numbness, or whether any lumps have been growing^[4].

To confirm the diagnosis, your doctor will need to take a biopsy (a small sample of tissue from the suspected tumor). This sample is sent to a specialist called a pathologist, who examines it under a microscope to determine if cancer cells are present^[1].

Your doctor will also order imaging tests to see the size and location of the tumor and to check if the cancer has spread. These tests might include^[1]:

• CT scans (computed tomography scans), which use X-rays and computers to create detailed pictures of the inside of your body
• MRI (magnetic resonance imaging), which uses magnets and radio waves to create images of soft tissues
• PET scans (positron-emission tomography scans), which can show areas of active cancer
• Ultrasound, which uses sound waves to create images

Because ACC is so rare, it can take some time to get a diagnosis. You might need several rounds of testing before doctors can confirm what type of cancer you have and begin treatment^[1].

Treatment options

The treatment for adenoid cystic carcinoma depends on where the tumor is located and whether it has spread to other parts of the body. Most treatment plans involve a combination of different approaches^[1].

Surgery

Surgery is the main treatment for ACC. The goal is to remove the entire tumor along with clear margins (some healthy tissue around the tumor)^[1]. This can be challenging because ACC tends to spread along nerves in ways that are hard to see. In some cases, the surgeon may need to remove lymph nodes or part of a nerve to ensure all cancer cells are removed^[1].

For tumors in the salivary glands near the skull base or brain, specialized surgeons may use advanced techniques such as endoscopic endonasal surgery, which goes through the nostril to reach the tumor while preserving important structures^[11].

Radiation therapy

After surgery, most patients receive radiation therapy (treatment using high-energy X-rays to kill cancer cells). This helps destroy any cancer cells that might have been left behind after surgery^[1]. Because ACC is known to spread along nerves, radiation is particularly important to target these areas.

Radiation therapy usually begins about four to six weeks after surgery. Treatment is typically given five days a week for about six weeks^[11]. If surgery is not possible because of where the tumor is located, radiation can be used as the main treatment, though it’s generally not as effective as surgery followed by radiation^[11].

Drug therapies

For advanced disease that has spread to other parts of the body, doctors may recommend drug therapies. These can include traditional chemotherapy (drugs that kill rapidly dividing cells) or newer targeted therapies (drugs that target specific features of cancer cells)^[11].

However, ACC tends to be less responsive to chemotherapy compared to many other cancers^[7]. Research is ongoing to find more effective drug treatments. Some of the drugs being studied target blood vessel growth (to cut off the tumor’s blood supply) or specific genetic changes found in ACC tumors^[7].

Outlook and survival

The outlook for people with adenoid cystic carcinoma depends on several factors, including the location of the tumor, its size, and whether it has spread. Overall, ACC has a relatively good survival rate in the first five years after diagnosis. About 89% of people survive at least five years^[6].

However, the long-term outlook is more challenging. One of the most concerning features of ACC is its tendency to come back, often many years after the initial treatment. Most people with ACC will experience recurrence (the cancer coming back) within five to ten years after treatment^[1]. In some studies, only about 40% of patients survived 15 years, reflecting deaths from late-occurring disease that spread to other organs^[6].

The slow-growing nature of ACC means that even when the cancer spreads to other organs, patients may survive for years. This is different from many other cancers, which tend to progress more rapidly^[6].

The importance of long-term monitoring

Because adenoid cystic carcinoma can come back many years after treatment, lifelong monitoring is essential. After you complete treatment, you’ll need regular check-ups and scans to watch for any signs that the cancer has returned^[1].

Your follow-up care will typically include physical examinations and imaging tests at regular intervals. Your doctor will create a monitoring schedule based on your individual situation. These appointments are important even if you feel well, because ACC can return without causing symptoms in the early stages^[1].

If the cancer does come back, catching it early through regular monitoring gives you the best chance for successful treatment. Your healthcare team will work with you to develop a follow-up plan that fits your needs and helps ensure any recurrence is detected as early as possible.