What causes one breast to be larger than the other?

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Q:

My 15-year-old daughter has one breast that is larger than the other. She is concerned that they will not even out. What can we do to check into this?

A:

This is a very common concern among female adolescents-even adult women! But it is quite common for each breast to be slightly different in size, a condition called asymmetry. Breast asymmetry is defined as a difference of form, position or volume of the breast, and it affects more than half of all women, so your daughter shouldn't feel alone. In fact, one study of 100 women who wanted breast augmentation with implants found that 88 percent had natural asymmetries.

Today, doctors can measure the symmetry of a woman's breasts via mammogram or, in your daughter's case, a special type of three-dimensional laser scanning called SCAN-3D, though these tests are not routinely available at most breast imaging centers.

Any discussion of the size or shape of a woman's breasts requires some rudimentary understanding of the anatomy of the breast itself. The breasts are actually glands contained within the front of the chest wall. The average breast weighs between seven and 10 ounces and is primarily composed of 12 to 20 lobes that spread out from the nipple like the spokes in a bicycle tire. These triangular lobes each have one central duct that opens at the nipple, through which milk exits.

Your breast tissue changes according to your menstrual cycle. For instance, you may find that your breasts feel fuller and are more sensitive when you're ovulating; and, in fact, they actually do get bigger because of water retention and additional blood flow. This is also when they're most likely to be the same size, however; one study found that breasts have the least amount of asymmetry on the first day of ovulation. During menstruation, breasts shrink again.

No one really knows what causes breasts to develop differently from one another, but possible contributors include hormonal changes or traumatic injuries. For instance, one report in the medical literature describes two cases of breast asymmetry that developed as the result of injuries the girls received to their "breast bud" area during gymnastics when they were 10 and 11.

Occasionally, an underlying medical or skeletal condition may cause asymmetrical breasts. One such condition, called juvenile, or virginal, hypertrophy of the breast, is a very rare problem in which one breast grows significantly larger than the other, leading to physical and psychological problems. It is typically treated with surgery.

Sometimes, underlying fibroids-non-cancerous tumors-may be the cause of asymmetry. Sudden or recent differences in breast size due to underlying breast masses should be evaluated by a breast surgeon. Other possible causes include scoliosis, or curvature of the spine, and deformities in the chest wall.

One thing your daughter should be aware of is that some research suggests that breast asymmetry may be a marker for women who have an increased risk of breast cancer. This is nothing to worry about now, but it should provide even greater incentive for her to conduct regular self breast exams throughout her life and, when the time is appropriate, obtain regular screening mammograms. Her doctors should also be aware of this asymmetry if it doesn't disappear as she gets older.

Generally, however, slight differences in a woman's breasts are of no concern. If the differences are greater than one bra cup, size, however, they may cause some psychological distress, particularly during adolescence, when a young woman's body and psyche are already changing so rapidly.

In the rare instance that the asymmetry causes such distress that your doctor recommends surgery, talk to the surgeon about breast reduction, rather than implants. Studies find that women with asymmetry who undergo reduction are generally more satisfied than those who have implants.

Have you ever looked into the mirror and felt concerned about why one of your breasts is bigger than the other? If yes, you’ve landed at the right place. Breast asymmetry is when one breast differs from the other in terms of size, volume, position or form. And it’s common. A woman’s breasts may fluctuate in size or volume for a variety of reasons including trauma, puberty and hormonal changes. Come let us find out more about unequal breast size.

Dr Tanaya Narendra, popular on social media as Dr Cuterus, gave her Instagram followers a sneak peek into the subject of breast size, which not many women up about.

The expert says that the phenomena is common. For most people, it’s the left breast which is bigger. But if your right breast is bigger, there’s nothing abnormal about it. This difference can be as large as one cup size and there’s nothing to be worried about.

Also read: Adopt these 6 habits for healthy boobs

Some likely causes of unequal breast size are:

1. Normal differences in growth

Most of our body parts are not perfectly symmetrical. This may include our legs, hair and eyebrows. So, the reason for your unequal breasts may be due to typical physiological variances which are beyond one’s control.

2. Period cycle

During each phase of your menstrual cycle, your breast tissue keeps changing. For instance, when you are ovulating, they could seem bigger and more sensitive. When menstruating, they contract.

3. Change in hormones

Even if both the breasts finish developing at the same time, it is quite possible that one breast may begin to develop before the other when hormones shift during puberty. So, it can be due to hormonal changes.

4. Traumatic injury

Breast asymmetry can result from injury to breast tissue before it has fully matured, possibly between the ages of 10 and 11 when adolescent girls go through the phase of puberty. Asymmetric breast growth may result from traumas to the chest such as some big injury, trauma, infection, or radiation.

5. A skeletal issue or some medical problem

One breast grows noticeably bigger than the other in a condition called juvenile or virginal hypertrophy of the breast, which is not that common. This medical problem frequently results in physical and psychological issues and is treated by a surgery.

According to Dr Narendra, a sudden change in the size of your breasts should raise an alarm, and you must visit a doctor in that case.

Check out her full video here!

Is breast asymmetry a symptom of breast cancer?

Breasts that are uneven are typically nothing to worry about. Regular scans are necessary to ensure that any breast abnormalities are found early, though. However, if the density of your breasts suddenly changes or if the asymmetry of your breasts varies very frequently, this could be a sign of breast cancer.

According to a 2015 research, women who have a breast asymmetry ratio of over 20 percent may be more likely to get breast cancer.

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