Mucous cyst
A mucous cyst is a painless, thin sac on the inner surface of the lips. It contains clear fluid.
Causes
Mucous cysts are common. They are painless, but can be bothersome because you are aware of the bumps in your mouth. The cysts are thought to be caused by sucking the lip membranes between the teeth. Mucous cysts are harmless. Left untreated, they can form a permanent bump on the inner surface of the lip. When mucous cysts occur on the floor of the mouth, they are called ranula. When they occur on the gum, they are called epulis. Mucous cysts may form around jewelry (piercings) on the lips or tongue. Symptoms A thin, fluid-filled sac appears on the inside of the lip. The sac is bluish and clear. It is painless, but it can be bothersome. The sac can also occur on the tongue, palate, inside the cheeks, floor of the mouth, or around tongue or lip piercings. Exams and Tests Your health care provider can usually diagnose a mucous cyst simply by looking at it. Treatment A mucous cyst often can be left alone. It usually will rupture on its own. Opening the top of the sac with a sterile needle will help it go away. If the cyst returns, it may need to be removed. To prevent infection and damage to the tissue, you should not try to open the sac yourself. This should be done by your health care provider. Oral surgeons and some dentists can easily remove the sac. Possible Complications There are usually no complications. When to Contact a Medical Professional If it becomes uncomfortable, have the cyst examined by your health care provider during a routine examination. Prevention There is no known prevention. Avoid intentionally sucking the cheeks or lips between the teeth. Alternative Names Mucocele; Mucous retention cyst; Ranula; Epulis Source: https://www.nlm.nih.gov/medlineplus/ency/article/001639.htm