A ganglionic cyst is a bump or mass that forms under the skin. Most commonly,
ganglionic cysts 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 tumours or cancerous.