A shower leak can be an especially difficult problem to have to deal with. If it is in your walls, again, that can result in substantial structural damage. If mold accumulates due to a leak, that is an even more expensive issue to repair.
When you call a professional, he will probably look for any loose tiles that may have formed mold. He’ll feel on the tile to see if the wall behind it is soft. That will probably mean there is wet drywall behind the tile. He will then likely cut away any damaged drywall discard it, and then remove the shower pan to make sure that is not the cause. If the pan is not the cause, he will find the pipe that is causing the leak and repair or replace it.
This repair could take quite a while because it will take some time to completely dry the area before the drywall can be replaced. Once that occurs, any tiles that have been removed will have to be replaced as well.