What is a Mucous Retention Cyst in the Left Maxillary Sinus?
A mucous retention cyst in your left maxillary sinus is a benign, fluid-filled lesion that is almost always harmless and typically requires no treatment. 1, 2
Nature of the Lesion
- Mucous retention cysts are benign lesions that appear as dome-shaped masses on imaging, typically arising from the sinus floor and filled with yellow serous fluid. 1
- These cysts are extremely common incidental findings on radiographic imaging, occurring in approximately 5.6% of patients undergoing sinus imaging. 3
- The cysts are self-limited and asymptomatic in the vast majority of cases. 2, 4
Natural Course and Prognosis
Most mucous retention cysts either spontaneously disappear or remain stable over time without causing any problems. 2, 4
- Long-term follow-up studies demonstrate that 41% of cysts completely disappear, 12% decrease in size, 24% remain unchanged, and only 29% increase in size over an average of 5 years. 4
- The natural history strongly favors a "wait and see" approach in the absence of complications. 4
When These Cysts Are NOT Harmful
You do not need any treatment or further investigation if: 5, 1
- The cyst does not interfere with the osteomeatal complex (the natural drainage pathway of your sinus)
- The cyst is located away from critical drainage areas
- You have no symptoms such as facial pain, nasal obstruction, or recurrent sinus infections
- The cyst occupies less than two-thirds of your sinus volume
When Intervention May Be Needed
Large cysts occupying two-thirds or more of the sinus volume may require treatment by an ear, nose, and throat specialist (otorhinolaryngologist) because they can potentially block sinus drainage. 5, 1, 2
Specific scenarios requiring attention:
- If you are planning dental implant surgery with sinus floor augmentation, small cysts can be safely drained during the procedure without affecting outcomes (96.8% implant survival rate). 1, 6
- If you develop symptoms like persistent facial pain, nasal obstruction, or recurrent infections, evaluation by an ENT specialist is warranted. 7
- Endoscopic removal has a low recurrence rate of only 3% when surgery is necessary. 6, 8
Common Pitfalls to Avoid
- Do not assume the cyst needs treatment just because it was found on imaging - most are incidental findings that never cause problems. 2, 4
- Do not ignore large cysts if you're planning dental procedures - they should be addressed before sinus floor augmentation to prevent drainage obstruction. 5, 1
- Always correlate imaging findings with your actual symptoms and medical history rather than treating the image alone. 5, 2
Bottom Line
Your mucous retention cyst in the left maxillary sinus is almost certainly harmless and requires only observation unless it is very large (occupying more than two-thirds of the sinus) or you develop symptoms. 2, 4 The American Academy of Periodontology confirms these lesions do not require investigation or treatment in most cases. 1