Residual breast tissue after mastectomy: how often and where is it located?

Background: Residual breast tissue after a mastectomy can lead to a (second) primary breast cancer. The development of breast cancer after prophylactic mastectomy and the finding of normal breast tissue around a local recurrence support this assumption. The aim of the present study was to investigate the prevalence and localization of residual breast tissue after a mastectomy.
Methods: A series of 206 women who underwent a mastectomy between January 2008 and August 2009 in 11 hospitals were enrolled onto this study after written informed consent was obtained. From each mastectomy specimen, a total of 36 samples were obtained from the superficial dissection plane at predetermined locations. The biopsy samples were analyzed for the presence of benign breast tissue in the inked superficial area. Differences in percentage of positive samples were analyzed by generalized estimating equations to account for their interdependence.
Results: A total of 7,374 biopsy samples from 206 breast specimens of 206 patients were included in the analysis. In 76.2 % of the specimens (n = 157), one or more positive biopsy samples were found. The positive findings were found diffusely across the superficial dissection surface of the specimen with a significant predilection for the lower outer quadrant and the middle circle of the superficial dissection plane.
Conclusions: After a mastectomy, there is a high probability of residual breast tissue. This tissue is predominantly located in the middle circle of the superficial dissection plane and in the lower outer quadrant. Surgeons should be aware of these locations so they may remove as much of the benign breast tissue as possible.