Fifth-placed Napoli thought they had gone ahead in the sixth minute when Eljif Elmas scored from close range after Genoa had repeatedly failed to clear a corner.
Yet, as Genoa were waiting to restart the game, the referee decided to review the incident on the pitchside monitor and finally disallowed the goal more than three minutes after the ball had entered the net.
Replays showed that ball had hit Napoli defender Kostas Manolas's fingertips before rebounding to Elmas although it did not appear to affect the flight of the ball.
Genoa nearly took a shock lead when Francesco Cassata saw his shot turned onto the post by keeper Alex Meret before Napoli went ahead in first-half stoppage time as Dries Mertens finished off a neat move by curling a low shot past Mattia Perin.
Genoa, who stayed in the relegation zone, levelled four minutes after halftime with the simplest of goals as Edoardo Goldaniga scored with a free header at the near post from a corner.
Napoli won it in the 66th minute when Fabian Ruiz launched a long ball over the Genoa defence to find Lozano and the Mexican forward known as "Chucky" timed his run perfectly and kept his cool to fire past Perin.