With the five-time Ballon d'Or victor failing to fond the back if the net in his latest outing against Cagliari, he lost further ground against the Lazio Striker who is now four goals clear of the 35-year-old.
Now, Ciro Immobile is on the top of the list with 35 goals in 36 matches, whereas Lewandowski is on the second position with 34 goals in 31 matches.
Lazio head into their final two Serie A fixtures of the season knowing that maximum points could secure second place in the standings.
Cristiano Ronaldo's hopes of finishing as Europe's top scorer were dealt a blow as he failed to score as champions Juventus were beaten by Cagliari.
Juventus, which won a record-extending ninth straight Serie A title on Sunday, fielded a much-changed team and lost 2-0 at Cagliari. Atalanta plays Inter in the final round of the season, when Lazio visits Napoli.
With 83 points, Juventus have a lead of four points over second-placed Inter Milan.
Zlatan Ibrahimović scored twice to help AC Milan win 4-1 at Sampdoria.
Ibrahimovic then nodded the ball across for Hakan Calhanoglu to add the second six minutes after the break.
It was the second time in three matches that the 38-year-old Ibrahimović has got a brace.
Ibrahimovic has scored nine league goals since rejoining Milan in January.
He also becomes the first player to have scored 50 goals for both Milan clubs, with 57 netted during his time at city rivals Inter from 2006 to 2009.
Both Lecce and Genoa will face Parma and Hellas Verona respectively at the weekend to avoid joining Brescia and SPAL in Serie B next season.