Segment S3 of the liver is the lower segment of the left outer lobe of the liver, and a cyst of segment S3 of the liver means that there is a liver cyst in the lower segment of the left outer lobe of the liver. Liver cysts are common benign lesions of the liver and are usually most common in congenital cysts. Depending on the location and size of the lesion, the clinical presentation of the patient varies. Smaller lesions are usually asymptomatic, while larger lesions can present with discomfort in the liver area and dull abdominal pain in the liver area. If combined with infection, fever and pain may also occur. For treatment, if the lesion is small and has no clinical symptoms, it can be reviewed regularly. If the lesions are large and present with compression symptoms, elective surgery is recommended.