ABSTRACT
The retention mucous cyst of the maxillary sinus is a benign lesion that occurs in the interior of the maxillary sinus due ductal obstruction. In the majority of the cases it is asymptomatic, and discovered on routine radiographic examinations. However, in some cases, this cyst can become large and cause symptoms as paresthesia, sensitivity to palpation, chronic headache, nasal blockage, and dizziness. Conservative treatment is conduct in most cases. Symptomatic retention cysts are treated by enucleation or curettage. Objective and case report: This study aimed to report a clinical case of symptomatic mucous retention cyst accidentally discovered in a patient treated by surgically-assisted rapid maxillary expansion. Conclusion: The curettage of the cyst allowed for the regression of symptoms and at 12 months postoperatively the patient is free of symptoms and no signs of recurrence of lesion were noted.