[724Skinsfan]

I just spoke with my dad who use to be a hospital laboratory director about what he thought would happen if the hospital were sued for damages resulting from a situation like yours. He said basically that a pathologist can not ever guarantee with absolute certainty that cells are cancerous. It's always opinion based and that the doctor should have conveyed to you that the diagnosis was a "best guess" based on what the pathologist sees. Most of the time they are right but it's not uncommon for this to happen.
In a nutshell, he's not sure but feels that you may lose out on the case so definitely clear it with your legal council about what you will have to pay regardless of the outcome.