Definitions of Abnormal Breast Size and Asymmetry: A Cohort Study of 400 Women

Macromastia, micromastia and breast asymmetry have an impact on health and quality of life. However, there is scarce information addressing breast size and asymmetry frequency distribution in reference populations.

The current study aims to identify factors that influence breast size and symmetry and classifies abnormal breast sizes and breast asymmetries in an adult German population.

Breast base dimensions, breast volume, symmetry, and other breast anthropometric parameters of 400 German female patients were determined in a retrospective review of the MRI archives at our institution. Professional medical MRI-segmentation software was used for volume measurement.

A total of 400 Patients were retrospectively enrolled. The patients had a mean age of 50 ± 12 years (min: 24; max: 82), mean BMI of 25.0 ± 5.0 (min: 14.7, max: 45.6), and a mean total breast volume of 976 ml (right: 973 ml, min: 64, max: 4777; left: 979 ml, min: 55, max: 4670). The strongest correlation of breast volume was observed with BMI (r = 0.834, p < 0.001), followed by breast base width (r = 0.799, p < 0.001). Smaller breasts have higher breast volume asymmetry ratios (r = - 0.124, p < 0.014). For a BMI between 18.5 and 24.9 kg/m², micromastia is defined by breast volumes below 250 ml (5th percentile) and macromastia by volumes above 1250 ml (95th percentile). Abnormal breast volume asymmetry (< 5th and > 95th percentile) is equivalent to an absolute difference of approximately 25% relative to the smallest side (bidirectional asymmetry ratio 5th percentile - 19%; 95th percentile 26%).

This study provides normative data of German women, as well as selected size-for-BMI percentiles and asymmetry ratio percentiles. The normative data may help to establish transparent and objective coverage criteria for health insurances.

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