I've also had multiple cancers, and not related to each other. Melanoma. Angiosarcoma, and a GIST. Also, and within a short time span, a large number of pre-cancer tumors which were surgically removed. That was a few years ago. Presently, I am having numerous skin cancers.
My doctors were not at all amazed or surprised, or even worried! But then, I had the bad luck of going to a very large teaching hospital where patient care was secondary and quite poor. Nevertheless, I managed to recover.
I do have a friend who is a cancer researcher in a cancer research facility; when I told him my history, he was sure it was no doubt a gene which gave me the pre-disposition for multiple cancers. He is interesting in testing, which is a lot more than my former doctors!