After two pancake flat days, Polanc (UAE Team Emirates) got in a breakaway group on the 158km stage 12 from Cuneo to Pinerolo, finishing just behind Benedetti (BORA-hansgrohe).
Benedetti had been dropped on the category one Montoso climb around 35km from the finish but worked his way back before sprinting to the biggest win of his career ahead of Damiano Caruso (Bahrain-Merida) and Eddie Dunbar (Team INEOS).
“I’m very happy. It’s a lot of emotion for a rider like me, It’s something I’ve waited for since the day I visited a start village of the Giro d’Italia in 1999. From that day, I dreamt of being a pro cyclist," Benedetti said.
"When I got dropped on the final climb, I thought it’d be normal if the three ahead would watch each other. I came across. After the last bend, it was a bit early to go to the front because of the wind but my legs were still responding.
"I didn’t celebrate before the line as I’ve learned from the under 17 category to not believe in the win too early and not to be too exuberant.”
Polanc, also in the breakaway group, arrived 25 seconds later then had a long wait to discover how much time the main bunch containing team-mate overall leader Valerio Conte (UAE and favourite Primoz Roglic (Jumbo-Visma) had lost.
He will move on to stage 13 with a four-minute seven seconds lead over Roglic with Conti another 44 seconds in arrears.
Polanc, who has won two career Giro stages, each time in the mountains, pulled on the pink jersey for the first time.
"It was a team tactic that I'd go in the breakaway so we could have better control over the race," he said. "It was also a way to keep the Maglia Rosa (pink jersey) in the team.
"We were lucky to be able to play these cards and I'm very happy to have the jersey. I was thinking about the stage win as well but being the virtual leader I had to pull a lot more than others."
Stage 13 covers 196km and contains several summits on a route that includes gradients of up to 15 per cent.
"It will be hard to still have the Maglia Rosa in Verona but at least I’ll try to retain it tomorrow. It’ll depend on how much energy I have left," Ploanc said.
"There’ll be even bigger gaps than now at the end. The Giro has just begun for GC riders. There’s a big battle to come.”
