A mucus cyst is a thin mucus-filled swelling on the oral mucosa. It is typically painless, and contains clear viscous fluid. It affects both sexes alike, and occurs at all ages. Most mucoceles tend to be only up to 1.5 cm in diameter.
A large proportion of mucoceles is associated with lip trauma, including biting the lip or sucking it. A sharp tooth may also cause damage or rupture to the salivary duct. Since most young children do not have teeth, mucoceles are rare in infancy.
More than 70 percent of oral mucoceles occur below the age of 20 years, in teenagers and children. There are exceptions, however, including the mucocele, which forms on the floor of the mouth, producing a swelling which makes the affected person resemble a bullfrog (species: Rana tigrina), with its inflatable chin air sacs, as far as the lower part of the face is concerned. For this reason, such a swelling is called a ranula. It occurs in people between 50 and 60 years. It is usually larger than other mucoceles. Retention mucoceles also occur later than other types, being most frequent above 30 years.
Mucoceles are thin-walled and typically painless domed swellings, occurring most frequently on the lower lip. While they are usually single, sometimes they may be multiple.
Other sites include the ventral (lower) surface of the tongue, the inside of the cheeks, and the palate.
The color of a mucocele may vary from pink to deep blue, depending on the degree of cyanosis in the tissue, vascular congestion, and the amount of fluid in the sac. Sometimes it is deep red due to bleeding into the lesion, especially in the deep variant of oral mucocele. Superficial mucoceles tend to be more transparent and bluish-white.
Oral mucoceles do not produce many symptoms apart from the palpable small swelling inside the mouth. However, very large or strategically placed mucoceles may cause obstruction of airflow, discomfort, speech difficulties, pain on mastication or problems with swallowing, and in very rare cases, breathing trouble because it blocks the throat. Sometimes it may produce an external swelling, if it is large enough and placed deeply. Ranulas are more likely to produce significant symptoms because of their location.
If the mucocele ruptures, it may result in a shallow area of erosion which is associated with mild pain. Healing is usually rapid. In some patients, the lesion may last longer, and has been uncommonly reported to last for up to three years.
Mucoceles are usually fluctuant because of their fluid content, but may sometimes drain periodically or be fibrosed, in which case the fluctuant feel is lost.