Adrien Costa of the Axeon Hagens Berman Cycling Team became the first American to win Le Tour de Bretagne Cycliste in its 50-year history Sunday while racing for USA Cycling's Under 23 squad.

The 18-year-old from Bend, Oregon, impressively soloed to win Thursday's queen stage of the race, then nursed an eight-second lead the next three days to land the biggest victory of his young career.

"It hasn't really sunk in because I wasn't thinking about the overall win as a true possibility," Costa said. "After I won that stage, I tried to enjoy that victory as much as possible. I didn't put too much pressure on myself for the overall win. Just being a first-year Under 23 rider, I was already happy to have won a stage. So that kind of helped me stay relaxed. I just can't believe it."