A mucous cyst of the oral mucosa is a swelling of connective tissue due to a ruptured salivary gland duct usually caused by local trauma. The mucocele has a bluish translucent colour, and is more commonly found in children and young adults.

The most common location to find a mucocele is the surface of the lower lip. Some mucoceles spontaneously resolve on their own after a short time. Others are chronic and require surgical removal. Recurrence may occur, and thus the adjacent salivary gland is excised as a preventive measure.