The bump on my wrist was diagnosed as a ganglion cyst. What is a ganglion cyst?

A ganglion is a small, harmless cyst, or sac of fluid, that sometimes develops in the wrist. Doctors don't know exactly what causes ganglions, but a ganglion that isn't painful and doesn't interfere with activity can often be left untreated without harm to the patient. However, treatment options are available for painful ganglions or ones that cause problems.