Pregnancy induced hyperplasia of residual breast tissue following risk reducing contralateral mastectomy - simply interesting or a clinically important observation.

After a diagnosis of breast cancer women with increased genetic risk often have a risk reducing contralateral mastectomy, and may opt for a nipple or skin sparing mastectomy with immediate reconstruction. A variable amount of residual breast tissue remains which may substantially increase in volume during pregnancy. Whether this increases later risk of breast cancer is unknown. We describe the clinical details of 3 patients with a history of unilateral breast cancer, including 2 with a BRCA mutation, who developed hyperplasia of residual breast tissue in the 3rd trimester of a later pregnancy. They all had a delayed contralateral risk reducing skin sparing mastectomy and immediate reconstruction. Pregnancy occurred some years later. We summarise their management, review the literature and raise questions for discussion. All developed prominent hyperplasia of breast tissue in the 3rd trimester that was clinically obvious asymmetrical breast swelling in the reconstructed contralateral breast. MRI demonstrated substantial breast tissue. The risk of breast cancer, particularly in those at high genetic risk developing in the residual breast tissue is unknown but in view of the volume, breast tissue was excised postpartum. This phenomenon of pregnancy induced hyperplasia of breast tissue after risk reducing mastectomy is not well described .There is residual breast tissue following a risk reducing subcutaneous mastectomy. The risk factors include age and skin flap thickness. MRI can demonstrate the residual breast tissue. Pregnancy induced hyperplasia of residual breast tissue may occur after risk reducing mastectomy with a hypothetical increased risk of subsequent breast cancer.