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Salivary gland cancer is a cancer that starts in one of the
salivary glands. It is not a single disease. There are actually several
different salivary glands found inside and near your mouth. Several
types of cancer and benign (non-cancerous) 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.
There are 3 major salivary glands, which occur in pairs:
- The parotid
glands, the largest salivary glands, are found on each
side of the face, just in front of the ears. About 7 out of 10 salivary
gland tumors start here. Most of these tumors are benign
(non-cancerous), but the parotid gland is still where most malignant
(cancerous) salivary gland tumors start.
- The submandibular
glands are smaller and are found at the back of the jaw.
They secrete saliva under the tongue area. About 1 or 2 out of 10
tumors start in these glands, and about half of these tumors are
benign.
- The sublingual
glands, which are the smallest, are found under the floor
of the mouth and below either side of the tongue. Tumors starting in
these glands are rare.
In addition, there are several hundred minor salivary glands
that are too small to see without a microscope. These glands are
located beneath the lining of the lips, tongue, hard and soft palate,
and inside the cheeks, nose, sinuses, and larynx (voice box). Tumors in
these glands are uncommon, but they are more often malignant than
benign.
Benign salivary gland tumors
Most salivary gland tumors are benign -- that is, they do not
spread from the salivary gland to other parts of the body and are
almost never life threatening.
There are several types of benign salivary gland tumors, with
names such as adenomas, oncocytomas, Warthin tumors, and benign mixed
tumors.
Benign tumors are almost always cured by surgery. Very rarely,
they may become malignant (cancerous) if left untreated for a long time
or if they are not completely removed and recur (grow back) several
times.
Only malignant
tumors of the salivary glands will be discussed further in this
document.
Salivary gland cancers (malignant salivary
gland tumors)
There are many types of salivary gland cancers. Normal
salivary glands are made up of several different types of cells, and
tumors can start in any of these cell types. Salivary gland tumors are
named according to which of these cell types they most look like when
viewed under a microscope. The main types of cancers are described
below.
There is also a wide range in how quickly salivary gland
cancers may grow and spread, with some types tending to grow faster
than others. Doctors usually give these cancers a grade (from 1 to 3,
or from low to high), based on how abnormal the cancers look under a
microscope. The grade gives a rough idea of how quickly the cancer is
likely to grow and spread.
- Grade 1 cancers (also called low grade or well
differentiated) look very much like normal salivary gland cells. They
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 and often grow
and/or spread quickly. The outlook (prognosis) for these cancers is
usually not as good as for lower grade cancers.
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. These cancers are usually low grade,
but they can also be intermediate or high grade. Low-grade
mucoepidermoid tumors have a much better prognosis than high-grade
ones.
Adenoid cystic carcinoma
Adenoid cystic carcinoma is the most common type of cancer in
the minor salivary glands. It is usually slow growing and often appears
to be a low-grade tumor. It is very hard to completely get rid of and
often comes back after surgery, sometimes many years later. The outlook
for patients with low-grade adenoid cystic carcinoma is much better
than for high grade tumors of this type.
Adenocarcinomas
Adenocarcinoma
is a term used to describe cancers that start in gland cells (cells
that normally secrete a substance). There are many types of salivary
gland adenocarcinomas.
Acinic cell
carcinoma: Most acinic cell carcinomas start in the
parotid gland. They tend to be slow growing. Although they are usually
low grade, how far they have invaded into nearby tissue is probably a
better predictor of a patient's prognosis (outlook).
Polymorphous
low-grade adenocarcinoma: These tend to start in the
minor salivary glands. These are usually low grade (as the name
implies) and are mostly curable.
Adenocarcinoma,
not otherwise specified: When viewed under a microscope,
these cancers have enough features to tell that they are
adenocarcinomas, but not enough detail to classify them further. They
are most common in the parotid glands and the minor salivary glands.
These tumors can be of any grade.
Rare
adenocarcinomas: Several types of adenocarcinoma are quite
rare. Many of these tumor types tend to be low grade and usually have a
very good outcome:
- basal cell adenocarcinoma
- clear cell carcinoma
- cystadenocarcinoma
- sebaceous adenocarcinoma
- mucinous adenocarcinoma
Other rare adenocarcinomas are more likely to be high grade
and may have a less favorable outcome:
- oncocytic carcinoma
- salivary duct carcinoma
Malignant mixed tumors
There are 3 types of malignant mixed tumors, carcinoma ex pleomorphic adenoma,
carcinosarcomas,
and metastasizing mixed
tumor. Carcinoma ex pleomorphic adenoma accounts for the
vast majority of these cancers. The other 2 are very, very rare.
Carcinoma ex pleomorphic adenoma is a cancer that develops from a
benign mixed tumor (also known as a pleomorphic adenoma). 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.
Other rare salivary gland cancers
Several other cancer types can develop in the salivary glands.
Squamous cell
carcinoma: This cancer occurs mainly in older men. It can
develop after radiation therapy for other cancers in the area. This
type of cancer tends to have a poorer outlook.
Epithelial-myoepithelial
carcinoma: This is a rare tumor. It tends to be low
grade, but it can recur after treatment or spread to other parts of the
body.
Anaplastic small
cell carcinoma: The cells in these tumors have nerve-like
features. These tumors are most often found in minor salivary glands
and tend to grow quickly.
Undifferentiated
carcinomas: This group of cancers includes small cell
undifferentiated carcinoma, large cell undifferentiated carcinoma and
lymphoepithelial carcinoma. These are high-grade cancers that often
spread. Overall, the survival outlook tends to be poor.
Lymphoepithelial carcinoma, which is much more common in Eskimo and
Inuit people, has a slightly better outcome.
Non-Hodgkin
lymphoma: These cancers start in immune system cells
within the salivary glands. They behave and are treated differently
than other types of cancer in the salivary glands.
This Detailed Guide is from http://www.cancer.org/.
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