In short
Adenoid cystic carcinoma of the salivary gland is a rare and unpredictable cancer that grows slowly but tends to return even after treatment. While this disease affects only a small number of people each year, understanding its nature, symptoms, and treatment options can help patients and families navigate the challenges it presents.
Key points
- Adenoid cystic carcinoma is a rare cancer affecting about 1,200 Americans yearly, primarily developing in salivary glands.
- The disease grows slowly but has a troubling tendency to return years or even decades after treatment.
- Unlike many cancers, ACC is not linked to smoking, alcohol, or other preventable risk factors.
- A painless lump in the mouth or face is often the first sign, though symptoms may not appear for a long time.
- ACC spreads along nerve fibers in microscopic ways that make complete removal during surgery extremely challenging.
- The disease affects slightly more women than men and is most commonly diagnosed between ages 40 and 60.
- Most ACC cases involve activation of the MYB gene, a discovery that is opening doors to potential targeted treatments.
- Long-term monitoring is essential for all ACC patients because recurrence can happen many years after successful initial treatment.
Understanding Adenoid Cystic Carcinoma
Adenoid cystic carcinoma, often shortened to ACC, is an uncommon type of cancer that starts in the salivary glands—the glands in your mouth and throat that make saliva to keep these areas moist. These tumors can look solid and round, or they might have holes in them, somewhat like Swiss cheese. Though ACC grows slowly compared to other cancers, it has a troubling habit of spreading along nerve pathways and returning many years after treatment.
The cancer primarily affects the major salivary glands, which include the parotid glands near your ears, the submandibular glands below your jawbone, and the sublingual glands under your tongue. However, ACC can also develop in the many smaller salivary glands scattered throughout your mouth, particularly in the roof of your mouth, at the base of your tongue, and along the lining of your throat.
What makes this cancer particularly challenging is its ability to exist in other parts of the body beyond the head and neck region. ACC can occasionally form in tear glands, sweat glands, breast tissue, the reproductive tract, skin, lungs, and even the windpipe. Despite these various possible locations, the salivary glands remain the most common site.
How Common Is This Disease?
Adenoid cystic carcinoma is genuinely rare. It makes up only about one percent of all cancers that develop in the head and neck region. In the general population, it affects roughly 4.5 out of every 100,000 people. In the United States, approximately 1,200 people receive this diagnosis each year.
Despite its rarity overall, ACC holds an important place among salivary gland cancers specifically. It is the second most common malignant tumor of the major salivary glands and the most common cancer of the minor salivary glands. When all salivary gland tumors are considered together, ACC accounts for about ten percent of them.
The disease shows a slight preference for women, who make up about 60 percent of cases compared to 40 percent in men. Most people diagnosed with ACC are between 40 and 60 years old, though the condition can occur at any age. Some studies note that it appears most frequently in people in their fifth to sixth decade of life, meaning between ages 50 and 70.
What Causes Adenoid Cystic Carcinoma?
The exact cause of adenoid cystic carcinoma remains unknown to medical experts. Unlike many head and neck cancers, ACC does not appear to be linked to lifestyle factors such as smoking or alcohol use. Researchers believe the disease develops because of genetic mutations—changes in the DNA of cells—that occur over time rather than being inherited from parents.
Scientists have discovered that a specific genetic event plays a key role in most cases of ACC. The activation of a gene called MYB appears to be the main driver of this cancer. Most commonly, this happens through a genetic rearrangement where the MYB gene fuses with another gene called NFIB. In some cases, the closely related MYBL1 gene becomes activated instead. These genetic changes tell cells to grow and multiply when they shouldn't, leading to tumor formation.
Age has been identified as an independent risk factor, meaning that getting older increases the chance of developing ACC. However, unlike some other cancers, there are no other clearly established risk factors. The disease does not run in families, and exposure to environmental triggers like pollution or asbestos may play a role, though this connection is not firmly established.
Who Is at Greater Risk?
Because the causes of adenoid cystic carcinoma are not well understood, identifying specific risk factors has proven difficult. The rarity of the disease means that only limited data from small studies is available. What is clear is that age matters—older adults, particularly those in middle age and beyond, are more likely to develop ACC.
Women face a slightly higher risk than men, though the reason for this difference is not known. The disease does not appear to be influenced by family history, meaning having a relative with ACC does not increase your own risk. Similarly, the lifestyle factors that raise the risk of other head and neck cancers, such as tobacco use and heavy alcohol consumption, have not been linked to adenoid cystic carcinoma.
Recognizing the Symptoms
One of the challenges with adenoid cystic carcinoma is that it often doesn't cause symptoms in its early stages. Because the tumor grows slowly, it can exist for quite some time before a person notices anything wrong. When symptoms do appear, they depend heavily on where the tumor is located and how large it has grown.
The most common first sign is a painless lump. This might appear inside the mouth, under the tongue, on the roof of the mouth, or inside the cheek. It could also show up as a small growth beneath the skin of the face or near the ear. Because these lumps typically don't hurt, people sometimes ignore them or assume they're not serious.
As the tumor grows or spreads, other symptoms may develop. Difficulty swallowing can occur if the tumor affects the throat area. Changes in voice or hoarseness might happen if the vocal cords or nearby structures are involved. Some people experience muscle weakness or a loss of sensation in the face, which occurs when the cancer spreads along nerve pathways—a characteristic behavior of ACC.
Breathing difficulties, particularly nasal congestion or trouble breathing through the nose, can signal that a tumor is present in the nasal passages or sinuses. Nosebleeds, though less common, are another possible symptom. Vision changes may occur if the tumor affects structures near the eye or involves the tear glands. Pain, while not always present initially, can develop as the cancer advances or presses on nerves.
Can Adenoid Cystic Carcinoma Be Prevented?
Unfortunately, because the exact causes of adenoid cystic carcinoma remain unclear and no lifestyle risk factors have been firmly identified, there are no known prevention strategies for this disease. Unlike lung cancer, which can often be prevented by not smoking, or skin cancer, which can be reduced through sun protection, ACC develops for reasons that are not within a person's control.
The genetic mutations that lead to ACC appear to happen randomly over time rather than being triggered by specific exposures or behaviors. This means that currently, there are no vaccines, supplements, dietary changes, or lifestyle modifications proven to reduce the risk of developing this particular cancer.
However, early detection remains valuable. Being aware of changes in your mouth or throat, and seeking medical attention for persistent lumps, difficulty swallowing, or other unusual symptoms can lead to earlier diagnosis. Regular dental checkups can help identify abnormalities in the mouth that might otherwise go unnoticed.
How the Disease Affects the Body
Understanding how adenoid cystic carcinoma changes normal body function helps explain both its symptoms and treatment challenges. At the cellular level, the genetic changes in ACC cells—particularly the activation of the MYB gene—drive uncontrolled cell growth and division. These cancer cells form a mass or tumor in the salivary gland tissue or other affected area.
One of the most distinctive and troubling features of ACC is perineural invasion. This means that cancer cells have a strong tendency to spread along nerve fibers. The cells essentially crawl along the protective covering of nerves, traveling away from the original tumor site. This can happen on such a microscopic level that it's extremely difficult for doctors to detect during imaging tests or even during surgery. This characteristic explains why ACC often returns after treatment—some cancer cells may have traveled along nerves to areas that weren't removed during surgery.
When ACC grows in the salivary glands, it disrupts the normal production and flow of saliva. A tumor in the mouth can make swallowing difficult by physically blocking the passage of food or by causing discomfort. If the tumor affects nerves that control facial muscles, it can lead to weakness or paralysis on one side of the face. Vision problems occur when tumors near the eye or in the tear glands interfere with normal eye function.
Unlike many other cancers, ACC doesn't frequently spread to lymph nodes—the small bean-shaped structures that are part of the immune system. Lymph node involvement occurs in only about 5 to 10 percent of cases. Instead, ACC tends to spread through the bloodstream to distant organs, most commonly the lungs and liver. This spread to distant sites is called metastasis, and it represents advanced or Stage 4 disease.
The slow-growing nature of ACC creates a unique pattern. People can live for years, even with metastatic disease, because the cancer cells divide and spread more slowly than those in many other cancers. However, this doesn't mean the disease is less serious—it simply follows a different timeline. The long survival even with metastases reflects that the cancer is generally well-differentiated, meaning the cells still somewhat resemble normal cells and grow more slowly.
At the molecular level, ACC has a relatively "quiet" genetic profile compared to other cancers. This means it doesn't have many additional genetic mutations beyond the key MYB or MYBL1 changes. This characteristic supports the idea that these specific genetic alterations are the main drivers of the disease. The MYB gene affects multiple cellular processes, including cell cycle control, DNA replication and repair, and how cells process genetic information.
