I don't know why they would have issued a 1099-MISC instead of W-2g; unless the winning didn't meet the criteria for issuing a W-2G.
However, I would treat the winnings and losses just as if it were a W-2G. Losses are itemized.
I would be very careful about trying to file a Sch C as a professional gambler. The standard to file in that status is very high, and would definitely create a red flag for audit.
This is a Supreme Court Case that lays out some of the criteria in which the Court found taxpayer to be a professional gambler.
COMMISSIONER OF INTERNAL REVENUE, Petitioner v. Robert P. GROETZINGER