Cancerous tumours of the salivary glands
A cancerous tumour of the salivary gland can spread, or metastasize, to other parts of the body. Cancerous tumours are also called malignant tumours. Many different types of tumours can develop in the salivary glands, but most are very rare.
It can be difficult to tell the difference between cancerous and non-cancerous tumours of the salivary glands because the cells look alike under a microscope. Cancerous salivary gland tumours will grow and spread into surrounding tissues and lymph nodes. Non-cancerous tumours rarely spread outside of the salivary glands.
Mucoepidermoid carcinoma (MEC) is the most common type of salivary gland cancer. Most are found in the parotid gland.
A MEC is made up of 3 different types of cells. There are mucin-secreting, epidermoid and intermediate cells in each MEC.
Adenoid cystic carcinoma
Adenoid cystic carcinoma is the 2nd most common type of salivary gland cancer. It is usually found in the minor salivary glands. This type of cancer often grows into and along the nerves of the face, which is called perineural invasion (PNI). It is generally slow growing, and though it doesn’t spread to the lymph nodes, it is not a curable cancer.
Adenoid cystic carcinomas can be made up of 3 types of cells. Most tumours have 2 or 3 different types of cells in them. Adenoid cystic carcinomas are divided into types based on the cells they have in them.
Cribriformadenoid cystic carcinomas have cancer cells surrounded by normal cells. Under the microscope, the tumour sample looks like it has a lot of holes. Cribriform is the most common form of adenoid cystic carcinoma. These tumours have a prognosis in between the solid and tubular types.
Solidadenoid cystic carcinomas have cells that look like solid sheets when examined under a microscope. They have the worst prognosis.
Tubular adenoid cystic carcinomas are made up of cells shaped like tubes. They have the best prognosis.
Any type of adenoid cystic carcinoma can come back, or recur, or spread to other parts of the body many years after it was treated.
Acinic cell carcinoma
Acinic cell carcinoma is usually slow growing with a fairly good prognosis. This type of tumour is usually found in children and in adults around the age of 50. It is most often found in the parotid gland. It can sometimes occur bilaterally (in both parotid glands at the same time).
Salivary duct carcinoma
Salivary duct carcinoma is a very aggressive type of tumour that can advance quickly. These tumours are found most often in the parotid gland. Symptoms start suddenly and can include pain and nerve problems, such as changes in feeling, drooling and muscle weakness.
In many cases, the cancer has spread to lymph nodes when salivary duct carcinoma is diagnosed. Even small tumours can spread to lymph nodes or different parts of the body.
Primary salivary gland lymphoma
Lymphoma that starts in the salivary gland, or primary salivary gland lymphoma, is rare. Most of these tumours are found in the parotid gland. The most common types are extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT lymphoma), diffuse large B-cell lymphoma (DLBCL) or follicular lymphoma. A surgical biopsy is done to confirm the diagnosis, and it is treated like a lymphoma.
Rare salivary gland tumours
The following cancerous tumours of the salivary glands are rare:
Mixed malignant tumours
Mixed malignant tumours contain different types of cancerous cells in the same tumour. The following are the main types of mixed malignant salivary gland tumours.
Carcinoma ex-pleomorphic adenocarcinoma is an aggressive tumour that starts out as a non-cancerous mixed tumour. It has a poor prognosis.
Very rare types
Other very rare types of salivary gland tumours include:
A type of cancer that starts in connective tissues (tissue that surrounds and supports various organs in the body).
The most common forms of sarcoma develop in bone, cartilage, fat, muscle or blood vessels.
A type of cancer that starts in epithelial tissues (a layer of cells that lines the body’s hollow organs and glands and makes up the outer layer of the skin).
The main types of carcinoma are adenocarcinoma and squamous cell carcinoma.
The most common forms of carcinoma develop in the prostate, breast, lung, colon, rectum and bladder.