Lengkepan kalimah di handap ieu: Dina 2017, Mastromatteo mangrupa bagian ti tim medali emas nu meunang 4x100 campuran medley di 2017 World Junior Swimming Championships. Dina taun 2019, Mastromatteo meunang 3 medali di
2019 Juara Dunia Junior di Budapest, kaasup medali pérak individu dina 50 m breaststroke.