Within the maxillary sinus, which lies beneath the cheek bone on each side, are mucous glands. A blockage in the mucous duct can cause the gland to enlarge, which can lead to the formation of a dome-shaped maxillary mucous retention cyst. The cyst does not usually cause any symptoms and does not damage, expand, or thin the wall of the sinus. For people who have chronic sinusitis, a high-resolution computerized tomography (CT) scan can detect the presence of a cyst.
To diagnose this type of cyst, medical professionals look for a dome-shaped spot with well-defined borders and a spherical outline on its outer edge on a CT scan. There is typically no damage to the bone, and it does not appear to have any connection to the roots of the teeth. This means that the cyst is not related to dental issues.
A maxillary mucous retention cyst can also be found on specialized dental X-rays because the sinuses sometimes need to be imaged because of how close they are to the bones and teeth. The high resolution of the CT scan can differentiate between the cyst and other growths that might be more serious. Different studies on how many people have retention cysts reveal different estimates, but experts believe they occur in about 10% of the general population. Individuals with pre-existing sinus conditions are slightly more likely to have this type of cyst.
Mucous retention cysts generally do not require any treatment unless they are blocking the openings to the sinus. A blockage in the ostiomeatal complex, where the maxillary sinuses open into the nasal cavity, can prevent the sinus from draining and leave the patient prone to infections. Surgery is required in this case, but only a small percentage of people with a mucous cyst need an operation to remove the blockage.
Although people with sinus conditions are more likely to have a cyst, an exact cause has not been found. Allergic reactions, a response to obstructions, or trauma are all probable causes, but the cysts are not found often enough with ostiomeatal complex obstructions to establish a link. There has not been any correlation with structural variations of this complex or any specific inflammatory disease. People with chronic sinus problems should be aware of possibly having a maxillary mucous retention cyst, but they are generally not a cause for alarm.