Salivary gland cancer is not a single disease. There are actually
several different salivary glands found inside and near your mouth.
Several types of cancer and benign (noncancerous) tumors can develop in
these glands.
About the Salivary Glands
Salivary glands produce saliva, which is the lubricating fluid found in
the mouth and throat. Saliva contains enzymes that begin the process of
digesting food. It also contains antibodies and other substances that
help prevent infections of the mouth and throat.
The 2 main types of salivary glands are the major salivary glands
and minor salivary glands.
The 3 major salivary
glands are the parotid
glands, submandibular
glands, and sublingual
glands. They occur in pairs. The parotid glands, the largest salivary
glands, are found on each side of the face, just in front of the ears.
The submandibular glands are smaller and are found on either side of
the neck, under the chin and tongue area. The sublingual glands, which
are the smallest, are found under the floor of the mouth and below
either side of the tongue. In addition, there are about 600 to 1,000 minor
salivary glands that are too small to see without a microscope. These
minor salivary glands are located beneath the lining of the lips,
tongue, hard and soft palate, and inside the cheeks, nose, sinuses, and
larynx (voice box).
About 80% of all salivary gland tumors begin in the parotid glands, 10%
to 15% start in the submandibular glands, and the rest develop in the
sublingual and minor salivary glands. Most tumors of the parotid and
submandibular glands are benign (noncancerous). Tumors in the minor
salivary glands (the smallest of salivary glands) are usually malignant
(cancerous). But, these are quite uncommon.
Types of Salivary Gland Tumors
Normal salivary glands are made up of several different types of cells;
tumors can start from any of the cell types. Salivary gland tumors are
named according to which of these cell types they most look like when
viewed under a microscope. The cancers are also given a numeric grade
of 1, 2, or 3 based on their appearance under a microscope.
- Grade 1 cancers (also called low grade or well
differentiated) look very much like normal salivary gland cells and
tend to grow slowly and have a good outcome.
- Grade 2 cancers (also called intermediate grade or
moderately differentiated) have an appearance and outlook that is
between grade 1 and grade 3 cancers.
- Grade 3 cancers (also called high grade or poorly
differentiated) look quite different from normal cells, often grow
and/or spread quickly, and have a poor prognosis or outlook.
Benign tumors do not spread from the salivary gland to other parts of
the body and are almost never life threatening. They are almost always
cured by surgery. Very rarely, benign tumors may become malignant if
left untreated for a long time or if they are not completely removed
and recur (grow back) several times. Only malignant (cancerous) tumors
of the salivary glands will be discussed in this document.
Mucoepidermoid carcinoma:
Most mucoepidermoid carcinomas start in the parotid glands. They
develop less often in the submandibular glands or in minor salivary
glands inside the mouth. They can be any grade. Low-grade
mucoepidermoid tumors have a much better prognosis than high-grade
ones.
Adenoid cystic carcinoma:
Adenoid cystic carcinoma is usually slow growing and often appears to
be a low-grade tumor. It is very hard to completely get rid of and very
often comes back after surgery. The outlook for patients with low grade
adenoid cystic carcinoma is much better than for high grade tumors of
this type.
Acinic cell carcinoma: Most
acinic cell carcinomas start in the parotid gland. They also tend to be
slow growing. Although they are usually low grade, their
grade is not the only factor useful in predicting their outcome.
Knowing how far they have invaded into nearby tissue is more helpful in
predicting a patient’s prognosis.
Polymorphous low-grade
adenocarcinomas: These tend to start in the minor salivary
gland sites, the tiny ones that are usually inside the mouth and are
too small to be seen without magnification. These generally are low
grade and are mostly curable.
Rare adenocarcinomas:
There are several other types of adenocarcinoma that are quite rare.
These are listed below.
- Basal cell
adenocarcinoma: Most people with this type have a good
outcome.
- Clear cell
carcinoma: People with this tumor have excellent outcomes
and deaths are rare.
- Cystadenocarcinoma:
This is generally a low-grade cancer and has a good outcome.
- Sebaceous
adenocarcinoma: About one-third of people with this tumor
are not cured.
- Oncocytic
carcinoma: This is very rare. It is usually a high grade
cancer.
- Salivary duct
carcinoma: This is also very rare. It occurs mainly in
older men. About half the time the cancer will come back and spread to
a distant site.
- Mucinous
adenocarcinoma: This is very rare and low-grade.
Malignant mixed tumors:
There are 3 types of malignant mixed tumors, carcinoma ex pleomorphic adenoma,
carcinosarcomas, and metastasizing
mixed tumor. The only one that occurs with any substantial
frequency is the carcinoma ex pleomorphic adenoma. The other 2 are
very, very rare. Carcinoma ex pleomorphic adenoma is a cancer that
develops from a type of benign salivary tumor called pleomorphic
adenoma or benign mixed tumor. This occurs mainly in the major salivary
glands. Both the grade and estimation of how far it has spread (stage)
are important in predicting its outcome. Approximately half of people
with these types of tumors will die within 5-10 years.
Other rare carcinomas:
Several other cancers can develop in the salivary glands.
- Squamous cell
carcinoma: This cancer has a poor outlook. About
one-fourth of patients survive 5 years. It occurs mainly in older men.
It often develops because of previous radiation therapy for other
cancers in the area.
- Epithelial-myoepithelial
carcinoma: This is a rare low-grade tumor.
Undifferentiated
carcinomas: This group of cancers includes small cell
undifferentiated carcinoma, large cell undifferentiated carcinoma and
lymphoepithelial carcinoma. These are all high-grade cancers that tend
to spread. Survival outlook is poor, except for the lymphoepithelial
type that has slightly better outcome. The lymphoepithelial type cancer
is also unique in that it is more common in Eskimo and Inuit peoples. Last Revised: 08/06/2006
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