Di Lorenzo winner takes Napoli five clear
Di Lorenzo, who had a goal disallowed in the first half, bundled the ball into the net in the 73rd minute after his initial effort had been saved, and it proved enough to take all three points at Stadio Diego Armando Maradona.
Lecce, despite its lowly position and dismal run of recent results, was far from outplayed by the league leader but fell to a fourth successive defeat and remains second from bottom in the standings with five points.
The home side's only real chance in the opening 45 minutes came close to half-time when Cyril Ngonge's effort from distance brought a save from Wladimiro Falcone, while Lecce's Federico Baschirotto also had a header saved by Alex Meret.
Napoli finally found a way through when Scott McTominay's header from a corner was parried away by Falcone and, while the keeper also got a hand to Di Lorenzo's first attempt from the rebound, Napoli's captain scrambled home at the second time of asking.
Lecce tried to push forward in search of an equaliser but a side which has scored just three league goals all season never seriously threatened Meret's goal and Napoli, while again far from convincing, earned the all-important three points.
