Definition of Cyst
A cyst is a closed pocket or pouch of tissue. It can be filled with air, fluid, pus, or other material.
Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc. – 10/28/2010