Ask The Experts

10-year-old's breasts are of uneven size

Q: My daughter is almost 10 years old. I have noticed that her left breast is obviously bigger than her right breast.

I took her to see a paediatrician about two years ago and was told that it is nothing of concern as long as she has not started menstruating.

Is this really normal and how it will affect her puberty?

A: The breast comprises glandular, fatty and fibrous tissue positioned over the pectoral muscles of the chest wall.

Breast development is the first sign of puberty in girls. This can occur from as young as seven to eight years old, or as late as 13.

With puberty, the female hormones, oestrogen and progesterone, stimulate further growth of ducts, fat and glandular tissue.

This growth continues until menstruation begins, typically two to three years from the onset of breast development, and slows down thereafter.

Your daughter is 10 years old. It is not unusual for her to have started puberty and, hence, her breasts may show some development.

Also, it is not uncommon to have unevenly sized breasts when she is going through puberty. They usually end up about the same size by the time puberty is completed.

She does not need treatment.

Occasionally, the cause of the asymmetry may be due to a lack of or underdeveloped breast tissue or pectoral muscles, or chest wall deformity.

But these are usually detected at birth or early childhood, and are often associated with other skeletal deformities. Very rarely, it may be due to a growth or a cyst.

Your doctor will be able ascertain the likely cause of asymmetry by checking her medical history and performing a physical exam.

Dr Siew Jia Xuan

Consultant in the department of general paediatrics and adolescent service at KK Women's and Children's Hospital

A version of this article appeared in the print edition of The Straits Times on November 24, 2015, with the headline '10-year-old's breasts are of uneven size AskTheExperts'. Subscribe