When a left maxillary sinus cyst grows large, symptoms such as chronic maxillary sinus inflammation symptoms on the left side, headache on the left side and discomfort in the left cheek, and intermittent flow of yellow fluid from the left side of the nose may occur. If the cyst is small, it is usually asymptomatic and can be detected on imaging. Mucous cysts are common in maxillary sinus cysts, mostly due to obstruction of the mucous glands and retention of secretions within the glands; the other may be due to inflammation or metaplasia, where the retained fluid exuding from the capillaries flows within the connective tissue of the submucosa. Sinus mucus cysts are often thought to be caused by blockage of the natural sinus openings of the sinuses, retention of secretions in the sinuses, and gradual formation of the maxillary sinuses, which are less common. Maxillary sinus mucous cyst is a common benign lesion, its occurrence and the maxillary sinus mucous gland duct mouth blockage, will cause chronic maxillary sinus inflammation symptoms, occasional persistent dull head pain, mostly located in the left forehead, there can also be the left cheek pressure or left upper teeth pain symptoms, can occasionally show intermittent yellow fluid from the left nasal cavity. If symptoms appear, patients should seek medical treatment in time, under the guidance of the doctor. When the symptoms are obvious, the treatment usually takes surgical excision treatment, which needs to be carried out under the nasal endoscopy to remove the maxillary sinus cyst. If there is no symptom or the cyst is small, regular review is needed.