Mucosal melanoma of the head and neck

by Jason Wasserman MD PhD FRCPC
August 4, 2022


What is mucosal melanoma?

Mucosal melanoma is a type of cancer that starts from a thin layer of tissue called mucosa. In the head and neck, mucosa is found inside the mouth (oral cavity), nose (nasal cavity), paranasal sinuses (maxillary sinus, ethmoid sinus, frontal sinus, and sphenoid sinus), and throat (pharynx and larynx). The tumour is made up of abnormal melanocytes.

What are the symptoms of mucosal melanoma?

The symptoms of mucosal melanoma vary depending on the area of the head and neck involved. Tumours that start in the nose (nasal cavity) or one of the paranasal sinuses can cause symptoms such as nasal congestion, runny nose, or frequent nose bleeds. Tumours that start in the mouth (oral cavity) frequently do not cause any symptoms although some patients may experience pain later in the disease. Tumours that start in the throat can cause voice changes such as hoarseness or difficulty breathing.

What causes mucosal melanoma?

Doctors do not know what causes most mucosal melanomas. However, people with a non-cancerous condition called mucosal melanosis appear to be at a higher risk of developing this type of cancer at some point in their lives. Unlike melanoma in the skin, mucosal melanoma in the head and neck is not caused by excessive exposure to UV light (such as the sun).

How common is mucosal melanoma?

Mucosal melanoma in the head and neck is a very rare disease that accounts for approximately 1% of all cases of melanoma. Most melanomas start in the skin.

How is the diagnosis of mucosal melanoma made?

The diagnosis is usually made after a small sample is the tumour is removed in a procedure called a biopsy. The tissue is then sent to a pathologist who examines it under the microscope. A second surgical procedure is then usually performed to remove the entire tumour.

What does mucosal melanoma look like under the microscope?

Mucosal melanoma is made up of abnormal melanocytes. Melanocytes are a specialized type of cell that can be found throughout the body. Melanocytes make a brown pigment called melanin and this pigment may be seen in the tumour. The cancer cells in the tumour may be described as epithelioid (round), spindled (long and thin), rhabdoid (similar to muscle cells), plasmacytoid (similar to immune cells called plasma cells), or clear (the cytoplasm, or body of the cell, looks clear). A type of cell death called necrosis and mitotic figures (cancer cells dividing to create new cancer cells) are also typically seen.

Mucosal melanoma of the head and neck
Mucosal melanoma of the head and neck. This picture shows a tumour in the oral cavity.

What other tests may be performed to confirm the diagnosis of mucosal melanoma?

Your pathologist may perform a test called immunohistochemistry to confirm the diagnosis. This test allows your pathologist to see specialized chemicals called proteins inside the cancer cells. The cancer cells in the tumour make the same proteins found in normal melanocytes. These proteins include S100, SOX-10, Melan-A, and HMB-45.

How is mucosal melanoma staged?

Your pathologist can only determine the tumour stage after the entire tumour has been removed. By definition, all mucosal melanomas of the head and neck are given a tumour stage (pT) of pT3 or pT4. A tumour is considered pT3 when it only involves the mucosa in one area of the head and neck. A tumour that grows into surrounding tissues including bones, large nerves, blood vessels, or the skin is considered pT4. The nodal stage (pN) is based on the examination of lymph nodes to look for cancer cells. If no cancer cells are found in any of the lymph nodes examined, the nodal stage is pN0. If cancer cells are found in any of the lymph nodes examined, the nodal stage is pN1. In cases where no lymph nodes were sent for examination by the pathologist, the nodal stage cannot be determined as is called pNx. Higher-stage tumours (those that are pT4 or pN1) are associated with a worse prognosis.

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