Late goal gives Atalanta win
Cigarini put the hosts ahead in the 41st minute with a long, low shot then provided the through ball for German Denis' winner in the 84th.
Lazio's 20-year-old Colombian forward Brayan Perea had equalized in the 53rd with his first Italian league goal.
Atalanta moved one point ahead of Lazio into a tie for sixth with Fiorentina, which faces two-time defending champion Juventus later.
Denis dedicated his goal to his mother with a specially prepared T-shirt, since it is Mother's Day in his home country of Argentina.