Alessandria became the first third-tier club to reach the Italian Cup quarter-finals in more than 30 years after beating Serie A side Genoa on Tuesday.
Alessandria, who beat Palermo in the fourth round, won 2-1 in extra-time.
Manuel Marras gave them the lead before Leonardo Pavoletti equalised in added time, but a 114th-minute Riccardo Bocalon goal won it for the visitors.
They are the first Lega Pro (the new name for Serie C) club to reach the last eight since Bari in 1983-84.
Bari went on to the semi-finals that season, eliminating Juventus and Fiorentina along the way.