Cysts

Definition:

A closed pocket or pouch of tissue; a cyst can be filled with air, fluid, pus, or other material.

Considerations:

Cysts may form within any tissue in the body. Cysts within the lung generally are air filled, while cysts involving the lymph system or kidneys are fluid filled. Migrating parasites such as trichinosis, dog tapeworm (toxocara canis), and echinococcus form cysts within muscle, liver, brain tissue, the lungs and the eye.

Cysts are common on the skin and develop as a result of infection, clogging of sebaceous glands, or around foreign bodies. They can also result from developmental abnormalities such as a pilonidal cyst (pilonidal dimple).