This is an excess of breasts of a man.
All men have a remainder of breast tissue which creates a small bump under the nipple, slightly raising the pectoral region. Many men have a significant amount of tissue which they consider unsightly.
An ultrasound can determine the proportion of fat and tissue making up the breast. With adolescents, it is advisable to seek an appointment with an endocrinologist to establish whether a hormonal abnormality is behind the excessive breasts.