A 2 Inch By 2 Inch Mass Literally Showed Up

A 2 inch by 2 inch mass literally showed up overnight. It is located on the right side under the rib cage, can this be a cyst or a hernia? It is my friend who has this and she said she went to a Dr who did an xray and another test. The Dr didn't know what it was and wants to do a CT scan next. Something doesn't sound right. Can you make a more educated diagnosis.