Adenoid Cystic Carcinoma Causes and Risk Factors

Adenoid cystic carcinoma (ACC) is a rare type of cancer that typically grows slowly but can spread over time. It often begins in glands that produce substances like saliva or mucus, most commonly in the head and neck. The exact causes of ACC are largely unknown, but researchers are studying genetic changes and other potential risk factors.

What is Adenoid Cystic Carcinoma Causes and Risk Factors?

Adenoid cystic carcinoma (ACC) is a rare form of cancer, meaning it is a malignant (cancerous) tumor that can grow and potentially spread to other parts of the body. It most often starts in the secretory glands, which are glands that produce substances such as saliva, mucus, or sweat.

ACC is a type of carcinoma, which is a cancer that begins in the epithelial cells that line organs and tissues. While it can develop in various locations, it is most frequently found in the major and minor salivary glands in the head and neck region. These glands are responsible for producing saliva. ACC can also occur in other areas, including the tear glands (lacrimal glands) in the eyes, the breast, skin, and respiratory tract. This cancer is known for its slow-growing nature, but it can be persistent and challenging to treat due to its tendency to spread along nerves (perineural invasion) and to distant sites (metastasis) over time. Metastasis often occurs years after the initial diagnosis and treatment, commonly affecting the lungs, liver, or bones. Understanding its characteristics is key to managing this complex condition.

Symptoms

Symptoms of adenoid cystic carcinoma depend on where the cancer starts in the body. Common signs can include a new, painless lump or swelling, persistent pain, numbness, or weakness in the affected area. These symptoms often develop slowly over weeks or months.

If ACC develops in the salivary glands, which is the most common site, you might notice a lump or swelling in your mouth, jaw, or neck. Other symptoms can include difficulty swallowing (dysphagia), changes in your voice such as hoarseness, or numbness or weakness in parts of your face. Pain in the affected area may also occur, though it is often not the first symptom. When ACC affects the tear glands, symptoms can include changes in vision, a bulging eye (proptosis), or pain around the eye. If the cancer starts in other less common locations, such as the breast or skin, you might feel a new lump or notice a change in the skin's appearance. It is important to remember that these symptoms can also be caused by many non-cancerous conditions, so a medical evaluation is essential to determine the exact cause.

Causes & risk factors

The exact causes of adenoid cystic carcinoma are largely unknown, and it is not strongly linked to common cancer risk factors like smoking or alcohol use. While specific reasons for its development are unclear, researchers are investigating genetic changes and other potential factors that might contribute to its formation.

Unlike many other cancers, ACC does not have clear, well-established risk factors related to lifestyle or environmental exposures. This means that most people who develop ACC do not have a history of smoking, heavy alcohol consumption, or other common cancer-causing habits. However, some research suggests that genetic changes may play a role. For example, specific gene fusions, such as the MYB-NFIB gene fusion, are frequently found in ACC cells. These are typically acquired mutations that occur during a person's lifetime rather than being inherited from parents. While prior radiation exposure has been investigated, it is not considered a strong or consistent risk factor for ACC. ACC can occur at any age, but it is most commonly diagnosed in adults, typically between 40 and 60 years old. Some studies indicate a slight female predominance, but this is not a definitive risk factor. Currently, there are no strong environmental links or dietary factors identified that significantly increase the risk of developing adenoid cystic carcinoma.

How it's diagnosed

Diagnosing adenoid cystic carcinoma typically involves a thorough physical examination, specialized imaging tests to visualize the tumor, and a biopsy. A biopsy, where a small tissue sample is taken, is crucial for confirming the diagnosis by allowing a pathologist to examine the cells under a microscope.

During a physical exam, your doctor will check for any lumps, swelling, or signs of nerve involvement, such as facial weakness. Imaging tests are then used to determine the tumor's exact size, location, and whether it has spread. These tests may include a computed tomography (CT) scan, which uses X-rays to create detailed cross-sectional images, or a magnetic resonance imaging (MRI) scan, which uses magnets and radio waves to produce detailed images of soft tissues. A biopsy is the definitive diagnostic step. This procedure involves removing a small piece of the suspicious tissue, often through a fine needle aspiration (FNA) or an incisional (part of the tumor) or excisional (entire tumor) biopsy. A pathologist then examines the tissue under a microscope to identify the characteristic features of ACC. In some cases, molecular testing on the biopsy sample may be performed to look for specific genetic changes, which can sometimes help guide treatment decisions.

Treatment options

Treatment for adenoid cystic carcinoma usually involves surgery to remove the tumor, often followed by radiation therapy to target any remaining cancer cells and reduce the risk of recurrence. Chemotherapy is generally less effective for ACC but may be considered for advanced or widespread disease.

Surgery is the primary treatment for ACC, aiming to completely remove the tumor along with a margin of healthy tissue around it. The complexity of the surgery depends on the tumor's location and size, especially if it is close to vital structures like nerves. Achieving clear margins (no cancer cells at the edge of the removed tissue) is crucial for a better outcome. Following surgery, radiation therapy is often recommended. This is known as adjuvant therapy and uses high-energy rays to kill any microscopic cancer cells that might have been left behind, thereby reducing the chance of the cancer returning in the same area. Radiation can also be used as the main treatment if surgery is not possible or if the tumor is inoperable. Chemotherapy, which uses drugs to kill cancer cells, is generally not very effective against ACC compared to other cancers. However, it may be considered for patients with advanced cancer that has spread to distant parts of the body (metastatic disease) or when other treatment options are limited. Researchers are also exploring targeted therapies that focus on specific genetic changes in ACC cells, and these may be available through clinical trials.

Recovery & outlook

The outlook for adenoid cystic carcinoma varies significantly based on factors like the tumor's location, size, and whether it has spread. While ACC often grows slowly, it has a notable tendency to recur locally and can spread to distant sites many years after initial treatment, requiring long-term follow-up.

Several factors influence the prognosis (outlook) for individuals with ACC. Tumors in smaller, more accessible glands generally have a better outlook than those in larger, more complex areas. The completeness of surgical removal, meaning whether all visible cancer was removed with clear margins, is also a critical factor. The stage of the cancer, indicating if it has spread to lymph nodes or distant organs, significantly impacts the prognosis. ACC is known for its slow but persistent nature. It can spread along nerves (perineural invasion) and to distant organs, most commonly the lungs, liver, and bones. This distant spread, or metastasis, can occur many years, sometimes even decades, after the initial diagnosis and treatment. Because of this risk of late recurrence and metastasis, long-term follow-up with regular check-ups and imaging scans is essential for people with ACC. Despite its challenging nature, many people with ACC live for a long time, especially with early detection and comprehensive treatment. Ongoing research continues to improve understanding and treatment options for this rare cancer.

When to see a doctor

You should see a doctor if you notice any new or persistent lump, swelling, pain, numbness, or weakness in your head, neck, or any other part of your body. Prompt medical evaluation is important for any unusual symptoms, even if they seem minor, to determine the cause.

Specific signs that warrant a doctor's visit include a new, unexplained lump or mass, especially in your mouth, jaw, neck, or near your eye. You should also seek medical attention if you experience persistent pain or discomfort in an area, numbness or tingling in your face or other body parts, or weakness in your facial muscles that makes it difficult to move parts of your face. Other concerning symptoms include difficulty swallowing, changes in your voice such as new hoarseness, or any changes in your vision, like a bulging eye. While these symptoms do not automatically mean you have cancer, they are signals that your body needs attention. Early diagnosis of any condition, including adenoid cystic carcinoma, can lead to more effective treatment and better outcomes.

Frequently asked questions

Is adenoid cystic carcinoma hereditary?

Adenoid cystic carcinoma is generally not considered hereditary. Most cases arise from genetic changes that occur during a person's lifetime, rather than being inherited from their parents. While specific gene mutations are found in ACC cells, these are typically acquired and not passed down through families.

How common is adenoid cystic carcinoma?

Adenoid cystic carcinoma is a rare cancer. It accounts for a small percentage of all head and neck cancers and an even smaller fraction of all cancers diagnosed each year. Its rarity means that specific incidence rates can vary slightly between studies, but it is consistently considered uncommon.

Can adenoid cystic carcinoma be cured?

Complete surgical removal of the tumor, especially when caught early, offers the best chance for a cure. However, ACC has a tendency to recur locally and can spread to distant sites years later, even after successful initial treatment. Long-term monitoring is crucial to manage the risk of recurrence.

What is the typical age for adenoid cystic carcinoma?

Adenoid cystic carcinoma can occur at any age, but it is most commonly diagnosed in adults. The typical age range for diagnosis is between 40 and 60 years old. It is less common in younger individuals and children.

Does adenoid cystic carcinoma spread quickly?

Adenoid cystic carcinoma is known for its slow growth. However, despite its slow growth, it has a tendency to spread along nerves and can metastasize (spread to distant parts of the body) years, sometimes even decades, after the initial diagnosis. This slow but persistent spread is a key characteristic.

What is the difference between adenoma and adenoid cystic carcinoma?

An adenoma is a benign (non-cancerous) tumor that originates in glandular tissue. It grows slowly and does not spread to other parts of the body. In contrast, adenoid cystic carcinoma is a malignant (cancerous) tumor that also arises from glandular tissue, but it has the ability to invade surrounding tissues and spread to distant organs.

Sources

• MedlinePlus — Adenoid Cystic Carcinoma Causes and Risk Factors
• Mayo Clinic — Adenoid Cystic Carcinoma Causes and Risk Factors
• Cochrane Library — Adenoid Cystic Carcinoma Causes and Risk Factors