You have many salivary glands in your mouth. They produce saliva. Saliva is made of water, mucus and enzymes.
Saliva moves from a gland into your mouth through tiny tubes called ducts. Sometimes, one of these tubes is cut. The saliva pools at the cut spot and causes a swelling, or mucocele. These swellings commonly occur inside the lower lip. They also can be found in other places inside the mouth, including the roof of the mouth (palate) and the floor of the mouth.
Swelling also can occur if one of these tubes is blocked and saliva backs up in the tube. If swelling occurs because the submandibular duct is blocked, the mucocele is called a ranula. A ranula is quite large and appears under the tongue.
Mucoceles occur only where you have salivary glands.
If you have a blue swelling that looks like a mucocele, your dentist may put pressure on it to see if it changes color (blanches). If it does, it may be a harmless growth made of blood vessels. This is known as a hemangioma.
Your dentist may take out the swollen tissue. It will be sent to a laboratory. The laboratory can tell if the tissue is a mucocele, or if it is something else. You may get an X-ray of the area. The X-ray will show if you have a salivary gland stone (sialolith). X-rays often are done for people who have ranulas.
A mucocele usually is removed by surgery. The dentist may use a scalpel or a laser to remove the mucocele. Afterward, the tissue will be sent to a laboratory for evaluation. There is a chance that after the mucocele is removed another one may develop.
Some doctors use corticosteroid injections before trying surgery. These sometimes bring down the swelling. If these work, you may not need surgery.