What is Adenoid Cystic Cancer?
Adenoid cystic carcinoma (ACC) is a rare type of cancer that mainly affects the glands that produce saliva, particularly the salivary glands. It makes up about 1% of all head and neck cancers. Yet, it’s the most common cancer found in the smaller salivary glands and the second most common in the larger salivary glands, accounting for 10% of all salivary gland tumors. ACC generally grows slower than other types of cancer. It tends to spread along nerves and can also spread to other parts of the body through the bloodstream. This type of cancer is most commonly seen in older people.
Due to its rarity, there’s not a lot of information about what causes it and how to manage advanced cases of the disease.
What Causes Adenoid Cystic Cancer?
The information about this type of cancer is scarce because it’s not very common. Only a few studies from single-center populations provide some insights into its causes. Unlike many other head and neck cancers like squamous and basal cell carcinoma, smoking and alcohol consumption have not been identified as risk factors for this cancer.
Researchers have discovered many genetic mutations after analyzing and sequencing more than 80 genomes of this cancer. According to these findings, age is a stand-alone risk factor that can increase the likelihood of developing this cancer.
Risk Factors and Frequency for Adenoid Cystic Cancer
Adenoid Cystic Carcinoma (ACC) is slightly more common in females, making up 60% of the cases compared to 40% in males. On average, there are about 4.5 cases per 100,000 people. Despite being usually found in the secretory cells of the salivary glands, ACC can also originate from different parts of the body, such as the hard palate, nasopharynx, tear glands, the tongue, and the external ear canal. There have also been cases of ACC in other areas, including the breasts, reproductive system, skin, and the windpipe. This condition typically affects older adults, with most cases showing up in people in their 50s to 60s, particularly when ACC appears in the head and neck area.
Signs and Symptoms of Adenoid Cystic Cancer
Adenoid cystic carcinoma (ACC) is a disease that usually doesn’t cause symptoms for a long time which can result in late medical help. The disease is often aggressive locally but can also spread to other parts of the body. ACC commonly presents as a slow-growing, hard, painless lump in the head and neck area. However, it can also cause pain and numbness as the tumor is known to invade the areas around nerves, especially in cases where the tumor is found in the parotid gland.
The specific symptoms can depend on the original location of the tumor and the nerve it inflicts. For example, if the tumor is in the nasopharynx, common symptoms can be frequent nosebleeds and an increasingly tight nasal cavity, all with a dysfunction of the tube connecting the ear to the throat. Tumors located near the base of the skull could result in issues with eye movement and weakness or paralysis of cranial nerves IX, X, XI, and XII. In some cases, Horner’s syndrome, a condition that impacts the face and eyes, has also been reported.
More than one third of these cases end up spreading to other parts of the body. The most common area for these distant metastases or spread to occur is the lungs, followed by the bones and liver. Rarely, the cancer can also reach the brain, although usually, any brain disease is due to the direct expansion of the tumor or it spreading along the cranial nerves.
Testing for Adenoid Cystic Cancer
Medical scans such as computerized tomography (CT) and magnetic resonance imaging (MRI) are often used to help determine the size and extent of the main tumor, as well as to understand its stage or severity. To definitively diagnose the disease, a biopsy of the tumor is needed. This involves testing a small tissue sample for certain characteristic features and markers. These markers include smooth muscle actin, S100, vimentin along with MYB and CD 117 (c-kit). These results help confirm the diagnosis.
Treatment Options for Adenoid Cystic Cancer
The go-to treatment for tumors is to completely remove them through surgery, when possible. When dealing with ACC (adenoid cystic carcinoma), a type of cancer that appears in the head and neck, it’s important to avoid cutting into nearby nerves and leave no cancerous tissues behind. If the cancer has spread to nodes in the neck, a surgical procedure called a modified radical neck dissection is usually the best choice. However, even with excellent surgical skills, cancer can return in about 75% of patients within 5 to 10 years.
In cases where cancer can be removed surgically but the margins of the tumor are positive (meaning that there is cancer at the edge of the tissue removed), the cancer has invaded a nerve, or there’s cancer in the lymph nodes, the outlook isn’t as good. Although there isn’t a one-size-fits-all rule, many medical centers recommend follow-up radiation therapy for these high-risk patients because studies have shown it can significantly decrease the chances of cancer returning locally. However, whether this post-surgery radiation treatments actually improve overall survival rates is still under debate.
This is because cancer can often return after 5 years in almost half of patients. Also, while radiation can stop the cancer from returning locally, it can’t prevent it from showing up in other parts of the body outside of the initial radiation area. Nevertheless, patients with intermediate or high-grade ACC or those who have positive surgical margins are usually recommended to go ahead with post-surgery radiation treatment. In cases when a tumor cannot be removed surgically, radiation therapy, along with other treatments, may be used, although these cases generally have less positive outcomes.
What else can Adenoid Cystic Cancer be?
Depending on where the tumor occurs, it might be necessary to determine whether it could be a harmful (malignant) or a non-damaging (benign) tumor of the affected organ. If the primary tumor is in the head and neck region, especially the salivary glands, doctors usually evaluate the following possibilities: pleomorphic adenoma, polymorphic adenocarcinoma, basaloid carcinoma, or mucoepidermoid carcinoma.
What to expect with Adenoid Cystic Cancer
Adenoid cystic carcinomas (ACCs) generally have a good outlook with about 75% of patients living for at least 5 years after their diagnoses. However, this number drops significantly with only 20% of patients reaching the 10-year survival mark. Certain characteristics impact the prognosis. For example, tumors larger than 4 cm or those in a solid formation can lead to a worse prognosis. There are also other factors such as nerve invasion and involvement of bones that can lead to unfavorable results and higher mortality rates.
Unfortunately, ACCs primarily originate in the head and neck region, and these areas contain many nerves and blood vessels (neurovascular bundles). This often makes the complete surgical removal of the tumor challenging and increases the likelihood of the tumor returning in the same area.
Possible Complications When Diagnosed with Adenoid Cystic Cancer
Tumors can originate from different regions and depending on where they come from, they might cause a variety of complications. Some of these include facial pain and paralysis, especially when the tumor is connected to the facial nerve. There might also be complications which occur during the surgical procedure to remove the tumor.
However, the most frequent issue is the return of the tumor. This tends to happen more commonly in patients that have large, distinct tumors, displaying lymphovascular infiltration (accumulation of fluid due to damaged lymphatic or blood vessels) or a positive nodal status (presence of cancer in lymph nodes).
Additionally, even those patients who have been diagnosed with ACC (adenoid cystic carcinoma) and had their tumor successfully removed at an early stage, are still at a high risk for distant metastases (spread of cancer cells from primary tumor to other body parts). This threat is particularly high for patients aged over 45, having lymph node involvement, or showing specific histological features like being of high-grade solid subtype.
The summary of these tumor complications is:
- Facial pain and paralysis
- Complications during tumor removal surgery
- Recurrence of the tumor – particularly in patients with large tumors and lymphovascular infiltration and/or positive nodal status
- Risk of distant metastases – especially in patients older than 45 years, with lymph node involvement, and high-grade solid subtype histological features
Preventing Adenoid Cystic Cancer
After being diagnosed, the patient should be informed that this type of tumor grows slowly but can aggressively spread within its local area. The appropriate treatment depends heavily on how advanced the tumor is. Most often, the tumor is surgically removed and then treated with radiation if there are high-risk factors. However, it’s crucial for patients to understand that there’s a chance that the cancer can come back, even more than five years after the initial surgery. Therefore, regular doctor’s visits for monitoring are strongly recommended.