A cyst is a closed, saclike structure that contains fluid, gas, or semisolid material and is not a normal part of the tissue where it is located. Cysts are common and can occur anywhere in the body in people of any age. Cysts vary in size; they may be detectable only under a microscope or they can grow so large that they displace normal organs and tissues. The outer wall of a cyst is called the capsule.
Cysts can arise through a variety of processes in the body, including
wear and tear or simple obstructions to the flow of fluid, infections,tumors,
chronic inflammatory conditions, genetic (inherited) conditions,
defects in developing organs in the embryo.
Most cysts arise due to the types of conditions listed above!
Until the doctor removes the "cyst" and sends it to be biopsied, you will not know what it contains (the lump). Once it is sent to be examined in a lab, the doctor will know a lot more about what caused your cyst and where it came from. I would follow the doc's advice at this point. Good luck and God bless.