Note that a cyst is a sac-like pocket of membranous tissue that contains fluid, air, or other substances. Cysts can grow almost anywhere in your body or under your skin. There are many types of cysts. Most cysts are benign, or noncancerous, but may be especially sensitive and require specific treatment. Always gather information from the client on the nature and inform them of how you will treat the cyst, including avoidance.