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