Redefining gigantomastia.

Gigantomastia is a rare but disabling condition characterised by excessive breast growth. Most definitions of gigantomastia refer to a particular weight of excess breast tissue. We speculate that in gigantomastia the weight of the breasts contributes significantly to the BMI, which has implications for healthcare rationing. This study aims to establish the contribution breast tissue makes to BMI in gigantomastia. In so doing, we propose a new definition of gigantomastia. Retrospective data was collected from the case notes of 68 females who underwent breast reduction or therapeutic mastectomy for gigantomastia. For the purposes of patient inclusion, gigantomastia is arbitrarily defined as excessive breast growth of over 1.5kg per breast. The difference between pre- and post-operative BMI is statistically significant (P<0.001). Mean pre-operative BMI is 38.7 with a mean specimen weight of 4506g. Mean contribution of specimen to body weight is 4.29%. There is no correlation between pre-operative body weight and the percentage contribution the breast resection specimen makes to body weight. Based on our data, we define gigantomastia as excess breast tissue that contributes 3% or more to the patient's total body weight, approximately one standard deviation below the mean. We suggest that the estimated excess breast tissue weight is taken into account when calculating pre-operative BMI in the gigantomastia population. The challenge of estimating excess breast weight pre-operatively may be met by 3D photography coupled with computer-assisted volumetry.