What is the statue of limitation on a mis diagnosis?

It will be two years on June 26 since he passed away. Our PCP kept prescribing antibiotics for sinus, when in fact it turned out to be cancer of the throat. My husband kept telling me that he would tell the doctor of his complaints each time he went for his visits. Which were frequent, every 90 day and then he switched him to every 6 months. The doctor kept saying that he didn't see anything in his throat and that maybe it was his sinus draining. He then gave him another antibiotic and said if that doesn't clear it up come back and see me. I had to get involved and insisted on getting a referral for my husband to see a specialist ENT. He continued to say that his throat doesn't look red or irritated. I insisted again for a ENT specialist. Well I finally got the referral got my husband in to see the specialist the first one said she wasn't 100% but that she used a scope in the office and said that it appeared to be a mass. She then referred me to another specialist and this doc