A mucoepidermoid neoplasm is a type of cancer found mainly in the salivary glands.

In rare cases, it also occurs in the lacrimal sacs (tear glands), the breasts, and the thyroid. Unusually among cancers, the tumor is made up of three different cell types: squamous cells, mucus-secreting cells, and intermediate cells. It may also be accompanied by small fluid-covered cysts, although it isn’t clear why.

The disease was first described in 1924 by Masson and Berger. Today, it is the most common type of salivary gland cancer, accounting for more than half of cases in children and 35% of cases in general.

Risk Factors

Doctors suspect that mucoepidermoid cancers arise from the mucus glands lining the digestive and upper respiratory tracts. This means that people with a history of respiratory or acid problems may be more at risk. The disease is more common in women than in men, and occurs more often in people over 50.

Signs and Symptoms

The first symptom is usually a hard, slow-growing bump in the cheek or jaw area. Benign tumors may be painless at first, but if the tumor is malignant, it can invade surrounding nerves and cause facial pain, numbness, or impaired motor function.

Diagnosis and Staging

If the mass can be accessed externally, the doctor will perform a biopsy to determine its nature and extent. Otherwise, CT or MRI scans may be used to locate the tumor before extracting cells for the biopsy. Additional tests may be performed to check for metastasis in the lungs, bone, liver, or brain.

If the tumor is found to be malignant, the next step is determining the stage or “grade” of the tumor. Mucoepidermoid cancers are classified into three grades:

Grade 1 (Low Grade): the tumor is small and slow-growing, and the cells resemble normal salivary gland cells
Grade 2 (Intermediate Grade): the tumor has started growing faster and the cells look slightly abnormal
Grade 3 (High Grade): the tumor is more aggressive and has already spread to other organs

Prognosis

The prognosis for mucoepidermoid cancer depends on the site and stage of the tumor. The overall survival rates are 92-100% for Grade 1 tumors, 62% to 92% for Grade 2, and 0% to 43% for Grade 3.

Treatment

Benign mucoepidermoid neoplasms can usually be treated with surgery. However, when the surgery cannot remove the entire tumor, the cancer can recur in a more aggressive or faster-growing form. Follow-up treatments may be given to prevent such cases.

For malignant tumors, the treatment of choice is a combination of surgery and radiation therapy. The surgery may remove the tumor, or in advanced cases, part or all of the salivary gland. Radiation therapy is used to kill any remaining cancer cells. If the cancer has spread to distant organs, the doctor may perform chemotherapy as well.

Prevention

Since the disease has been linked to digestive and respiratory problems, people who are predisposed should get regular screening. Those who fall into one or more high-risk categories should also be tested at least once a year to detect abnormal growths.