A ganglion cyst is a bump or mass that forms under the skin. Most commonly, ganglions
are seen on the wrist (usually the back side) and fingers, but they can also develop on
the shoulder, elbow, and knee. These form when tissues surrounding certain joints become
inflamed and swell up with lubricating fluid. They can increase in size when the tissue is
irritated and often can "disappear" spontaneously. These masses or cysts appear
to grow sometimes but they are not tumors or cancerous.