Downtown crowds cheered Italy's Stefano Oldani home as he broke clear for his first professional win on stage 12 of the Giro d'Italia on Thursday, while surprise Spaniard Juan Pedro Lopez held the leader's pink jersey.

Oldani was too fast for fellow breakaway riders Lorenzo Rota and Gijs Leemreize after a breakaway on a high-speed 204km romp from Parma, across the Appenine mountains and north to Genoa.

After making it two wins in two days for Italy, an euphoric Oldani said he joined the early breakaway to aid teammate Mathieu van der Poel, a fan favourite due to his peloton-splitting attacks, but who missed the cut on the last climb as three riders broke off from an original group of 20 escapees.

Stars for the day, the three were cheered home along a festive town centre route.

"I wanted it so badly," said the 24-year-old.

"When I realised that I'd won a stage on the Giro there was a wave of emotion that I couldn't hold back."

The race was conducted at breakneck speed with 53km covered in the first hour, the winner crossing the finish line 30 minutes ahead of even the fastest prediction.

Giro rookie Lopez held the race lead for a ninth day, nursing his advantage from his escape to Mount Etna on stage 4.

"Luckily the weather conditions are my favourites, like at my home in south of Spain," Lopez said, with Italy enjoying warmer than usual May weather.

"Nine days in the Maglia Rosa is a lot! But I wouldn't mind some more."

- Tight at the top -

Lopez rolled across the finish line with the main contenders 09min 08sec after Oldani.

Less than 20 seconds separate a clutch of potential Giro winners with Richard Carapaz of Ineos Grenadiers, Mikel Landa of Bahrain Victorious and Romain Bardet of DSM the most credible candidates.

In a rare occurence Wilco Kelderman hauled himself back into the overall reckoning reckoning gaining eight minutes as part of the escape to make up for his meltdown on the Blockhaus mountain last Sunday.

Australian sprinter Caleb Ewan left the Giro empty handed ahead of the stage when he became the 14th rider so far to drop out.

Ewan fell on day one and failed to add to his five stage wins here on previous editions.

Along the route for stage 12 the Giro remembered Belgian sprinter Wouter Weylantdt on the Apennine Passo del Bocco, where he died during a stage in 2011.

Friday's stage 13 is a largely flat 150km run from San Remo to Cuneo, where a sprint finish is the most likely outcome.

Over the weekend Saturday's treacherous hilly stage should shake up the standings while Sunday's mountain climb is a slog to a summit finish at over 1500m at Cogne in the Aosta Valley north of Turin.