How can I find out what cancer a family member had before they passed away?

I’m on a search for information on the death of a family member.
My grandfather passed away in 1987. He was diagnosed with cancer in 1982, after years of heart attacks starting at age 36..he gets cancer :(
He had an extremely rare cancer, so rare they say only about 6 people had the cancer before him.
I’ve tried googling, but I’m not exactly sure what to look for. And his name isn’t really helpful, because I doubt when it was documented they used his name.
Is there any way to find out this information? It seems to be more curiousity than anything.
Also, I believe he died in Texas or maybe Florida. He wasn’t married to my grandmother, so the facts are hazy for me.
Thanks for any information!