Salivary gland cancer starts in any of the glands that make saliva. Other than three major pairs of salivary gland, the human body has over 600 minor ones, which are present throughout the lining of the mouth and throat. The salivary glands produce spit which helps keep the mouth and throat moist. They help swallow and digest food as well. They also protect the teeth and keep the mouth and throat from infections. There are two types of salivary glands:

• Major salivary glands: There are three main pairs of major salivary glands. They are the parotid glands, which is located under the lobes of the ears; sublingual glands, which are under the tongue; and the submandibular glands found under each side of the jawbone.
• Minor salivary glands: Other than those, over 600 smaller, minor salivary glands can be found throughout the lining of the throat and mouth.

Cancer in the salivary glands starts in the parotid glands. Approximately, around 80% of salivary gland cancers begins here. Just over 10% start in the submandibular gland, while the rest begin in either the sublingual glands or in the minor glands. Sometimes, it is common to have a non-cancerous (benign) lump in these glands. Around 75% of tumors in the parotid gland are benign. Meanwhile, 50% of the tumors found in the submandibular gland are also said to be benign.

Sublingual gland tumors are rare. Many different types of cells are found in the salivary glands. Cancer can start in any one of these cells. The type of salivary gland cancer will depend on the cell type and its origin:

1. Mucoepidermoid cancer
The cells that line the salivary glands are the mucoepidermoid cells. Cancer of this type is usually tiny and filled with mucus. These cancers develop mostly in the parotid glands but can also develop in the submandibular gland. They could also develop in the minor salivary glands. This cancer is slow in growth (low grade), but sometimes they can also be fast-growing (high grade).

2. Acinic cell carcinoma
This type of cancer develops in the acinar cells, which produce saliva and are slow-growing. It is found most commonly in women.

3. Adenoid cystic cancer (ACC)
About 15% of salivary gland cancers are adenoid cystic cancers. This is one of the most common types of minor salivary gland cancers. It is usually low grade and begins with a painless lump.

4. Adenocarcinoma
This is a rare type of cancer. They develop in the epithelial cells either in the major or minor salivary glands.

5. Malignant mixed cancers
This type of cancer is similar to most common non-cancerous tumors of the salivary glands. Usually, only in a small percentage of people, this benign tumor goes on to develop as malignant mixed cancer.

6. Polymorphous low-grade cancers
These are slow-growing cancers where the cancerous tissues have a variety of different growth patterns. They are rare and the second-most common cancer of the minor salivary glands.