How do a cyst and an abscess differ?

Several : A cyst is a lesion that has an inner cavity lined with epithelial cells abscess means the presence of pus. A chronic cyst may become acute( infected) at which time the central cavity fills with pus. This is then referred to as an abscess.

Abscess vs cyst: An abscess is a local acute infection (usually of bacterial origin) that contains puss. A cyst is a walled off cavity usually filled with fluid or semi-fluid material. Cysts can become infected. All abscesses warrant immediate treatment and coverage with antibiotics. There are many types of cysts (traumatic, developmental, etc) and not all of them require treatment.