The forward will undergo a minor heart procedure over the next few days to resolve a congenital defect which saw him hospitalised at the weekend.
"His career is not at risk," the Rossoneri official stated on Wednesday afternoon.
"He'll need a few months to recover, but he'll probably have to wait between four and six months to get clearance to play. It'll be the doctors who decide.
"All I know for sure is that he is missing football a lot, but I've told Cassano that we'll keep his place warm."