Surgical Planning

Breast Asymmetry: Causes and Correction

UNE Plastic Surgery · Dr. Kim Uigeon, board-certified plastic surgeon · Published 2026-09-21 · Updated 2026-09-21

1. The five causes of asymmetry

A left-right difference is common. Measuring volume on the mammograms of 174 healthy women, 55% had a larger left breast (Senie et al., Cancer, 1980).^[2] So before asking whether there is a difference, look at where it came from.

• Congenital developmental difference: one breast developing less at puberty.
• Chest-wall asymmetry: the rib shape itself differing.
• Scoliosis: the spine curving, so breast position differs.
• Change after pregnancy and breastfeeding: when one side was fed from more.
• Change after prior surgery: such as benign-tumor excision.

The correction method differs by cause, so an accurate diagnosis is the starting point.

2. The criteria for diagnosis

On examination, both standing and lying positions are assessed, since the difference can look different by posture. The criteria for considering correction:

• Breast volume difference: 50 cc or more
• Nipple position difference: 1 cm or more
• Fold position difference: 1 cm or more
• Inter-nipple distance difference: 5 mm or more

Any one of these alone can make a difference visible, so it is assessed precisely with preoperative photos, measurement, and a chest X-ray. A large volume difference is not seen as a purely cosmetic matter. A study compared the left-right volumes of 446 healthy women and 201 breast-cancer patients (Kayar & Çilengiroğlu, Breast Cancer: Basic and Clinical Research, 2015):^[1] a difference exceeding 50 mL, or exceeding 20% of the smaller side, was more common in the cancer group (odds ratio 2.18 for the 20% threshold). It is a retrospective study, so it is not a causal number, and the authors noted that prospective confirmation is needed — but it is grounds to advise adding imaging if the difference has grown recently.

3. Correction options

There is an approach that touches only one side and one that adjusts both together; the choice depends on which is prioritized. By the degree and cause of asymmetry:

• Different-size implants left and right: when a volume difference is the main issue.
• A lift on one side only: when the degree of ptosis differs.
• Fat grafting: for fine contour adjustment.
• Nipple and areola repositioning: when the nipple-position difference is large.

4. The limits of the result

This must be settled before surgery. If the chest wall itself differs left and right or the spine is curved, there is a limit to how far an implant can match them — knowing this at the start gives far more satisfaction with the result. An important point: even after correcting breast asymmetry, perfect left-right symmetry is difficult. If the chest wall itself differs or the spine is curved, some difference can remain. Setting a clear expectation at the pre-op consultation about “how far it can be matched” is the key to satisfaction.

Summary

• Asymmetry must be accurately diagnosed by cause first.
• Correction options are applied in steps by the degree of asymmetry.
• Perfect left-right symmetry is difficult. If a difference has grown recently, review it with imaging.

References

1. Kayar R, Çilengiroğlu ÖV. Breast volume asymmetry value, ratio, and cancer risk. Breast Cancer (Auckl). 2015;9:87–92. doi:10.4137/BCBCR.S32789. (446 healthy vs 201 cancer; asymmetry >20% odds ratio 2.18; retrospective.)
2. Senie RT, Rosen PP, Lesser ML, et al. Epidemiology of breast carcinoma II: factors related to the predominance of left-sided disease. Cancer. 1980;46(7):1705–1713. doi:10.1002/1097-0142(19801001)46:7<1705::aid-cncr2820460734>3.0.co;2-h. (174 women; 55% larger on the left.)