Adenoid cystic carcinoma of salivary gland – Diagnostics – Overview of Information and Clinical Research

Diagnosing adenoid cystic carcinoma of the salivary gland is a multi-step process that often requires careful examination and specialized testing. Because this cancer is rare and grows slowly, it can be challenging to identify, sometimes taking multiple rounds of evaluation before reaching a clear diagnosis. Understanding what tests are involved and what to expect can help patients and their families navigate this complex journey with greater confidence.

Introduction: Who Should Undergo Diagnostics

If you notice a painless lump in your mouth, particularly under your tongue, inside your cheek, or near your jaw, it is important to see a doctor. Adenoid cystic carcinoma often begins as a slow-growing mass that does not cause discomfort at first, which can make it easy to overlook.^[1] Sometimes people experience symptoms such as trouble swallowing, a hoarse voice, nasal congestion that does not go away, nosebleeds, or changes in vision. If these signs persist or if you develop numbness or pain in your face, seeking medical attention is advisable.^[4]

Because adenoid cystic carcinoma is rare and its symptoms can be vague or resemble other, more common conditions, doctors might not immediately suspect cancer. This is why it is important to speak up if something feels wrong or if a lump does not go away after a few weeks. Early evaluation can lead to earlier diagnosis, which is important given that this cancer has a tendency to spread along nerves and through the bloodstream.^[1]

People between the ages of 40 and 60 are most commonly diagnosed with this condition, and it occurs slightly more often in women than in men.^[1] However, adenoid cystic carcinoma can appear at any age. Unlike many other head and neck cancers, it is not linked to smoking or alcohol use, and there are no known lifestyle-related risk factors.^[2] This means anyone experiencing unexplained symptoms in the head, neck, or mouth area should consider getting checked, regardless of their personal habits or family history.

⚠️ Important

Because adenoid cystic carcinoma grows slowly, it may not cause symptoms until it has already grown significantly or spread. This makes regular checkups and prompt evaluation of any unusual lumps or persistent symptoms especially important. Even if a lump feels painless, it should still be checked by a healthcare provider.

Diagnostic Methods

Diagnosing adenoid cystic carcinoma begins with a thorough examination by your doctor. They will review your medical history and ask about your symptoms, including when you first noticed the lump, whether it has grown, and if you have experienced any pain, numbness, or difficulty swallowing. Your doctor will also examine your mouth, face, and neck, looking for lumps and checking the movement of your jaw and facial muscles.^[4]

During the physical exam, the doctor will feel for swollen lymph nodes, which are small bean-shaped structures that help your immune system fight infection. They are located around your neck, behind your ears, and under your jaw. Although adenoid cystic carcinoma does not spread to lymph nodes as often as other cancers, it can happen in about 5% to 10% of cases, so checking these areas is an important part of the examination.^[1]

Biopsy

If your doctor suspects adenoid cystic carcinoma, the most important diagnostic test is a biopsy. A biopsy involves taking a small sample of tissue from the suspicious lump or growth so that it can be examined under a microscope by a specialist called a pathologist.^[1] The pathologist looks at the cells in the tissue sample to determine whether they are cancerous and, if so, what type of cancer it is.

There are different ways to perform a biopsy. In some cases, a needle is used to remove a small piece of tissue. In other situations, a larger sample may be needed, which might require a minor surgical procedure. The type of biopsy used depends on the location and size of the lump. The biopsy is essential because it provides a definitive diagnosis and helps distinguish adenoid cystic carcinoma from other types of tumors or non-cancerous conditions.^[1]

Imaging Tests

In addition to a biopsy, your doctor will likely order one or more imaging tests to see the size and location of the tumor and to check whether the cancer has spread to other parts of your body. Imaging tests create detailed pictures of the inside of your body and help doctors plan the best treatment approach.^[1]

Common imaging tests used in the diagnosis of adenoid cystic carcinoma include:

CT scans (computed tomography scans): These use X-rays taken from different angles and combined by a computer to create cross-sectional images of your body. CT scans can show the size and location of the tumor and whether it has spread to nearby structures.^[1]
MRI (magnetic resonance imaging): This test uses powerful magnets and radio waves to create detailed images of soft tissues in your body. MRI is particularly useful for looking at tumors in the head and neck because it can show how the cancer may be affecting nerves. Because adenoid cystic carcinoma has a tendency to spread along nerve fibers, MRI images are often analyzed carefully to trace nerve pathways all the way up to the brainstem.^[1]^[6]
PET scans (positron-emission tomography scans): These involve injecting a small amount of a radioactive substance into your body, which is absorbed by cancer cells. The PET scanner detects this substance and creates images that show areas of high metabolic activity, which may indicate cancer. PET scans are sometimes combined with CT scans to provide more detailed information.^[1]
Ultrasound: This test uses sound waves to create images of the inside of your body. It is sometimes used to examine lumps in the salivary glands or other soft tissues.^[1]

These imaging tests help doctors see not only the primary tumor but also whether the cancer has spread to distant organs such as the lungs or liver, which are common sites for metastasis in adenoid cystic carcinoma.^[1] The combination of biopsy results and imaging findings gives doctors a complete picture of the disease, which is critical for planning treatment.

Challenges in Diagnosing Adenoid Cystic Carcinoma

Because adenoid cystic carcinoma is so rare, it can take time to reach a diagnosis. You may need several rounds of testing or consultations with different specialists before the cancer is identified.^[1] The slow-growing nature of the tumor and the lack of early symptoms can also contribute to delays. Additionally, the appearance of adenoid cystic carcinoma under the microscope can vary, making it challenging for pathologists to identify. This is one reason why it is sometimes referred to as having “heterogenous histopathology,” meaning the tissue looks different in different cases.^[5]

Another diagnostic challenge is that adenoid cystic carcinoma can spread along nerves in a way that is hard to detect. This is called perineural invasion, and it happens when cancer cells creep into the nerve fibers surrounding the tumor at a microscopic level. Because this spread is so small, it may not show up clearly on imaging scans or be visible during surgery.^[1] This is why MRI scans are often used to follow nerve tracts and check for signs of cancer extending beyond the main tumor.

Diagnostics for Clinical Trial Qualification

If you are considering participating in a clinical trial, which is a research study that tests new treatments, you will need to undergo specific tests to determine whether you are eligible. Clinical trials have strict criteria for enrollment to ensure that the treatment being studied is tested in the right group of patients and that participants are safe throughout the study.

The diagnostic tests required for clinical trial qualification are similar to those used in standard diagnosis but may be more detailed or specific. For example, you will typically need a confirmed biopsy showing that you have adenoid cystic carcinoma. The biopsy sample may also be tested for specific genetic or molecular features of the tumor, such as the presence of certain mutations or protein markers.^[6]

Recent research has shown that most cases of adenoid cystic carcinoma are driven by changes in a gene called MYB. This gene becomes overactive in the cancer cells, often because it fuses with another gene called NFIB as a result of a genetic rearrangement. Testing for this MYB-NFIB fusion or for MYB overexpression may be part of the diagnostic workup for some clinical trials.^[6] Other studies might look for mutations in genes like NOTCH1 or test for the expression of certain receptors that could be targeted by new drugs.^[7]

In addition to tissue testing, you may need imaging scans such as CT, MRI, or PET scans to assess the extent of the disease. These scans help determine the stage of the cancer, which is an important factor in deciding whether you are eligible for a particular trial. Some trials are designed for patients with early-stage disease that has not spread, while others focus on advanced or metastatic cancer.^[7]

Blood tests may also be required as part of the screening process for a clinical trial. These tests check your overall health, including the function of your kidneys, liver, and bone marrow. This information helps researchers ensure that you are healthy enough to tolerate the experimental treatment and that the treatment will not cause harmful interactions with other medical conditions you may have.

⚠️ Important

Participating in a clinical trial can provide access to new treatments that are not yet widely available. However, not all patients will qualify for every trial. The specific tests and criteria vary depending on the study. If you are interested in clinical trials, talk to your doctor about whether this option might be right for you and which studies you may be eligible for.

Because adenoid cystic carcinoma is so rare, there are ongoing efforts to develop better treatments through clinical research. Some trials are testing new drugs that target specific pathways involved in the cancer’s growth, such as inhibitors of the MYB gene or therapies that block blood vessel formation to starve the tumor of nutrients.^[7] Other studies are exploring combinations of existing drugs or new approaches like cancer vaccines designed to train the immune system to attack the tumor.^[7]

To be considered for a clinical trial, your doctor will need to provide detailed information about your diagnosis, including pathology reports, imaging results, and your medical history. This information is reviewed by the research team to determine if you meet the study’s eligibility requirements. Even if you do not qualify for one trial, there may be other studies available that are a better fit for your situation.

Prognosis and Survival Rate

Prognosis

The outlook for patients with adenoid cystic carcinoma varies depending on several factors, including the size and location of the tumor, whether it has spread, and how well it responds to treatment. One of the defining characteristics of this cancer is that it is slow-growing but persistent. While many patients live for years after diagnosis, the cancer has a strong tendency to come back, even after successful treatment.^[1]

Most people with adenoid cystic carcinoma will experience recurrence, meaning the cancer returns, within five to ten years after their initial treatment. In some cases, the cancer can come back many years later, which is why lifelong monitoring with regular scans and checkups is necessary.^[1] Late recurrences are particularly common with this type of cancer, and patients may face multiple rounds of treatment over their lifetime.^[5]

The cancer’s ability to spread along nerves and through the bloodstream affects prognosis. When cancer cells invade nerve fibers, a process called perineural invasion, they can travel to areas that are difficult to treat, such as the base of the skull or the brain.^[1] When adenoid cystic carcinoma spreads to distant organs, most commonly the lungs and liver, it is considered metastatic or Stage 4 disease, which is more serious.^[1] However, even with metastatic disease, some patients can live for many years because the cancer tends to grow slowly.^[6]

Survival rate

Adenoid cystic carcinoma has a relatively high five-year survival rate, meaning that a large percentage of patients are still alive five years after diagnosis. Survival rates can be as high as 89% at five years.^[6] However, survival drops significantly over time. By fifteen years after diagnosis, the survival rate may fall to around 40%, reflecting the high rate of late recurrences and the challenges of managing this disease over the long term.^[6]

It is important to understand that survival rates are statistical averages based on large groups of patients and do not predict what will happen to any individual person. Many factors influence survival, including how early the cancer is detected, the specific characteristics of the tumor, and how well it responds to treatment. Advances in surgery, radiation therapy, and emerging treatments are continually improving outcomes for patients with adenoid cystic carcinoma.

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