Careful. Ganglion cysts in children tend to act differently than in adults. Also, cysts that show up on the back of a child's hand or wrist may need a different strategy than ones that develop on the front.
A recent study suggests that most painless ganglion cysts in children go away by themselves. The authors studied 14 children with simple ganglion cysts. These kids ranged in age from two to about nine years old. With no other treatment than watching and waiting, all but three (79%) of the cysts went away by themselves within one year from the time the doctor first saw them. The two cysts that didn't go away had formed on the back of the hand, called dorsal cysts. The authors caution that dorsal cysts may need special attention and possibly other treatment strategies.
You are advised to have your doctor examine your daughter's cyst. Recommendations can be given based on how long she's had the cyst, and whether your doctor feels treatments other than observation are needed.