Is it possible for a girl to be born without breasts?

Absence of the breast: A rare condition wherein the normal growth of the breast or nipple never takes place and they are congenitally absent. Absence of the breast, also called amastia, is frequently not an isolated problem.

What is Hypomastia?

Hypoplasia (or hypomastia), defined as breast size of 200 mg (mL) or less in an adult female, represents a significant decrease in size of breast tissue relative to standard breast size adjusted for age and developmental status. Hypoplasia of mammary tissue may be unilateral or bilateral.