Mucoepidermoid carcinoma, or MEC, is the most common form of salivary gland cancer. It arises from the cells lining the salivary ducts and represents about 30% of all cancers found in these glands. This type of cancer is characterized by a diversity in its behavior; some tumors are slow-growing and localized, while others can be more aggressive and spread. While it is most often associated with the salivary glands, it can develop in other areas of the body containing similar glandular tissues.
Common Locations and Symptoms
Mucoepidermoid carcinoma most frequently develops in the major salivary glands. The parotid glands, located just in front of the ears, are the most common site. Tumors can also appear in the submandibular glands below the jawbone and the sublingual glands under the tongue. The initial sign is often a slow-growing, painless lump or swelling in the cheek or jaw.
Beyond the major glands, MEC can originate in the minor salivary glands lining the mouth and throat. The palate is a frequent location, but tumors can also be found on the tongue, lips, and inner cheeks. Symptoms might include a persistent sore or a lump. Depending on the tumor’s position, a person might experience difficulty swallowing or speaking.
When a tumor affects a major salivary gland near the facial nerve, it can lead to symptoms like numbness, persistent pain, or weakness in the facial muscles. While rarer, MEC can also occur in other mucus-producing glands, such as the lacrimal gland that produces tears or the bronchi inside the lungs.
The Diagnostic and Grading Process
Confirming a diagnosis of mucoepidermoid carcinoma begins with imaging. A physician may order a Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scan. These techniques create detailed pictures of the head and neck, allowing doctors to see the tumor’s location, size, and if it has grown into nearby structures like nerves or bone. A Positron Emission Tomography (PET) scan may also be used to check if the cancer has spread.
The definitive step for diagnosis is a biopsy, where a small sample of tumor tissue is collected for examination. A common method is a fine-needle aspiration (FNA), where a thin needle is inserted into the lump to withdraw cells. A surgeon may also perform an incisional biopsy to remove a piece of the tumor or an excisional biopsy to remove the entire lump.
A pathologist examines the biopsy sample to determine the tumor’s grade: low, intermediate, or high. This classification describes how abnormal the cancer cells appear and how quickly they are likely to grow. Low-grade tumors contain cells that look more like normal cells and tend to be slow-growing. High-grade tumors are composed of abnormal-looking cells that are more likely to grow quickly and metastasize.
In addition to grading, doctors use the TNM staging system to describe the cancer’s extent. This system assesses the size of the primary Tumor (T), whether cancer has spread to nearby lymph Nodes (N), and if it has Metastasized (M) to distant parts of the body.
Primary Treatment Modalities
The main treatment for mucoepidermoid carcinoma is surgery. The goal is the complete removal of the tumor along with a surrounding layer of healthy tissue, known as a clear surgical margin, to reduce the chance of recurrence. The specific type of surgery depends on the tumor’s size and location, such as a parotidectomy for a tumor in the parotid gland.
During surgery, special attention is paid to the facial nerve, which runs through the parotid gland and controls facial movements. Surgeons make every effort to preserve this nerve to avoid complications like facial weakness. If cancer may have spread to the lymph nodes, a neck dissection may be performed to remove them.
Following surgery, radiation therapy may be advised. This treatment uses high-energy rays to destroy any cancer cells that might have been left behind. Adjuvant radiation is recommended for patients with:
- High-grade tumors
- Large tumors
- Cancer that has spread to lymph nodes
- Surgical margins that were not clear
Chemotherapy has a limited application and is not an initial treatment for MEC. It may be an option for cancers that have metastasized to distant organs or for recurrent tumors that cannot be treated with surgery or radiation.
Outlook and Long-Term Monitoring
The outlook for mucoepidermoid carcinoma is closely tied to the tumor’s grade and stage. Patients with low-grade tumors detected early have a favorable prognosis, with a 5-year survival rate of approximately 98%. These tumors are often managed successfully with surgery alone.
The prognosis for intermediate-grade and high-grade tumors is more varied. The 5-year survival rate for high-grade MEC is around 67%. Comprehensive treatment, which may include surgery and radiation, is often required for these more aggressive cancers.
After treatment, long-term monitoring is necessary to watch for any signs of recurrence. These follow-up appointments include a physical examination of the head and neck by a specialist.
This surveillance also involves periodic imaging scans, like CT or MRI, to check for new tumor growth. The frequency of these check-ups is higher in the first few years after treatment and then becomes less frequent over time.