There was also a dramatic finale at Torino where Ciro Immobile and Alessio Cerci both scored in stoppage time to beat Genoa 2-1.
Alberto Gilardino came off the bench to give the visitors an 85th-minute lead but Immobile levelled with a curling shot in the 92nd minute, his 19th goal of the season, and Cerci scored from a similar position one minute later.
AC Milan, languishing in mid-table after a dismal season, continued their improvement by winning their fourth game in a row as Riccardo Montolivo’s long-range strike sealed a 1-0 win over bottom club Catania.
Leaders Juventus (84 points) visit Udinese on Monday (1845) and second-placed Roma (79) beat Atalanta 3-1 on Saturday.
They are followed by Napoli (67) in the Champions League playoff spot with Fiorentina (58) and Inter (53) in the Europa League places.
At the bottom, Chievo’s win lifted them to 16th with 30 points while Bologna, who drew 1-1 at home to Parma, are next with 28, leaving Livorno (25), Sassuolo (25) and Catania (20) increasingly isolated in the relegation zone.
Inter forward Mauro Icardi set off the fireworks at Sampdoria when he scored against his old club in the 13th minute and provoked his former team mates with his celebration.
Jeered before kickoff, the Argentine turned to the Sampdoria fans and put his hand to his ear as if encouraging them to insult him, angering the home players.
The next twist came in the 18th minute when Sampdoria won a penalty but Maxi Lopez, who had refused to shake hands with Icardi before the game, saw his kick saved by Samir Handanovic.
Two minutes later, Sampdoria forward Eder was booked for a blatant dive which sparked a scuffle in which the Brazilian was given another yellow card and sent off.
Undeterred, Samp pushed forward, forcing several world class saves from Handanovic but they ran out of steam after halftime and Inter romped home with a Walter Samuel header, another Icardi goal and Rodrigo Palacio’s 15th goal of the season.
The win lifted Inter, hoping to avoid the ignominy of missing out of European football for a second successive season, back into fifth place which earns a Europa League spot.
Walter Mazzarri’s side had failed to win in their previous four outings, all against lower-placed opponents.
Napoli, who have been exasperatingly inconsistent all season, fell behind to a well-taken Senad Lulic goal but came to life when Dries Mertens scored with a superb long-range strike four minutes before halftime.
The game turned three minutes after the re-start when Lazio captain Lorik Cana gave away a penalty, was sent off and Higuain converted.
The Argentine struck again with a half-volley in the 66th minute and completed his hat-trick with a clever chip in stoppage time after Eddy Onazi had replied in between for Lazio.
Alberto Aquilani scored twice and Juan Cuadrado, Borja Valero and Alessandro Matri, from a penalty, were also on target for Fiorentina while Jacopo Sala, Luca Toni, from another penalty, and Juan Iturbe replied for Verona in an eight-goal thriller.
Toni’s goal, against the team who let him go at the end of last season, took his tally to 17 for the campaign.
(Reporting By Brian Homewood, editing by Ed Osmond)