Elevated platelets have many causes. Has he had any treatment yet? For me, it was because i had cancer treatment and it did not rebound to its level of the past.
If there is a portal at the oncologist office, use it. If he is readying for treatment or ending, this question has different reasons. I had MDS after BC and that was when i noted my platelets did not recover. I have a TP53 mutation. Has your husband had a genetic test? Not sure why you would be told it is a mutation without a name for it.