Left maxillary sinus cysts belong to the sinus cysts, in addition to sinus mucosal cysts, no matter how large should be operated; sinus mucosal cysts such as cause clinical symptoms of patients need surgical resection, smaller asymptomatic can be without surgical resection. Left maxillary sinus cysts are categorized as mucus cysts, mucosal cysts, pneumatocysts, odontogenic cysts, and dermatocysts. With the exception of sinus mucous cysts, all other types of cysts, regardless of size, require surgical removal or surgical facilitation of drainage. This prevents the gradual enlargement of the cyst and thus the symptoms such as displacement of the eyeballs, headache, eye pain, facial lumps, nasal congestion, runny nose, and loss of smell. Sinus mucous membrane cysts, for small cysts asymptomatic, may not need to be removed; cysts often grow to a certain extent can be ruptured and disappear on their own. However, for patients whose cysts are large enough to cause symptoms, it is also necessary to undergo radical maxillary sinus surgery or endoscopic surgery to remove the cysts. Patients are advised to go to the hospital and make the decision of whether or not to undergo surgery after the doctor has assessed the extent of the condition, without delay, to avoid adverse consequences.