Napoli ended a three-game winless run in Serie A with a victory at AC Milan that saw them move above the hosts and within four points of leaders Inter.
Elif Elmas headed in at the front post from a corner after five minutes to score what proved to be the winner.
Franck Kessie thought he had levelled for the hosts at the San Siro in the 90th minute but after a lengthy check it was chalked off for a tight offside.
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