N'afọ 2017, Mastromatteo so na ndị otu meriri ọlaedo na 4x100 mixed medley na 2017 World Junior Swimming Championships
Ọ dị mma. N'afọ 2019, Mastromatteo nwetara ihe nrite 3 na 2019 World Junior Swimming Championships na Budapest, gụnyere ọlaọcha ọlaọcha n'otu n'otu na 50 m breaststroke.