No melanomas that I have ever seen ever present like a ganglion cyst. My husband has had one removed from the top of his wrist. Twice. it is about the size of a half a ping pong ball, it bothered him only when playing baseball as the glove strap cuts across it. Surgery was not fun (general) and it came back.
Shawn if you are still concerned over cancer try to not think of it as always being so. It will def drive you nuts. I had a sebacceous cyst on my cheek it was huge, (never thought it was anything other than that) most melanomas and I say MOST (not all) present totally unlike a hard cyst. If I may ask I have forgotten your stage of cancer what is it?
Take care of yourself.