Spaniard Juan Pedro Lopez took the overall lead of the Giro d'Italia on Tuesday as Lennard Kamna won stage 4 after they nursed a large lead up a 23km climb to a summit finish on Mt Etna in Sicily.
The two stars of the day had been part of a long-range breakaway that started the climb six minutes ahead of the chasers.
The overall favourites Richard Carapaz and Simon Yates whittled that lead down to just 2min 37sec as part of a group of the big guns including Romain Bardet and Mikel Landa.
Lopez of Trek-Segafredo now leads Bora's Kamna by 39sec in the overall, with Yates fourth at 1min 42sec and Carapaz of Ineos 11th at 2min 06sec.
"I don't care how much my lead is, I just want to savour the moment," Lopez said. "I don't know how long I can keep it (the leader's pink jersey)," he added.
This was the seventh time the Giro has climbed Etna and the 25-year-old Kamna can add this famous victory to his mountain stage win on the Tour de France in 2020.
"Lopez had some kind of problem on the last corner and I just about got it. Now I can continue this Giro with confidence," Kamna said.
After a three-day stay in Hungary, the Giro peloton had a rude awakening on its arrival in Italy as a 14-rider escape group tore away early on the 170km ride from Avola to Etna.
Among the potential contenders for the overall title, the 2017 Giro winner Tom Dumoulin dropped time on the final climb as British outfit Ineos set a blistering pace up the 1,892m summit.
"I can't explain it, but it was unpleasant to be alone on the climb," said Dumoulin of Jumbo.
Another rider who failed to produce was Italian veteran double Giro winner Vincenzo Nibali, who was dropped in the final kilometres.
Overnight leader Mathieu van der Poel made no effort to defend his lead on the climb, but had earlier attempted a long range solo escape.
Astana's Colombian climber Miguel Angel Lopez withdrew early in the stage on a day marked by a motorbike crash that brought a clutch of riders tumbling to the tarmac.
Wednesday's stage 5 is also in Sicily, running from Catania to Messina with a mountain to climb early on, making another escape a strong possibility.