A young woman concerned about small breast size

Case scenario

Karen is 18 years old and presents because she is concerned about the small size of her breasts. She says that her breasts started to develop in her first year at high school but then seemed to stop growing, although she started menstruating at the age of 13 years and has had regular periods ever since. On examination, it is noted that she is very tall (180 cm), has a body mass index of 23 kg/m² and normal pubic and axillary hair and a normal female perineum. Her breasts show minimal development, with budding equivalent to Tanner Stage 2 of puberty. Karen has no other health concerns and is fit and active.

What should be the approach to Karen’s concern?