Can Oncologic Safety Be Married to a Predictably Viable Mastectomy Skin Flap?
David L. Larson, MD, Zainab Basir, MD, Timothy P. Bruce.
Medical College of Wisconsin, Milwaukee,, WI, USA.
Since the introduction of the skin-sparing mastectomy (SSM) 20 years ago, the technique, broadened reconstructive options, and enhanced results have been widely recognized. Additionally, the oncologic safety of SSM is established, in spite of the fact that we know that no mastectomy removes all breast tissue and local recurrences very rarely occur within the skin flaps of the mastectomy. But, as the surgical technique for SSM has gained widespread acceptance, there is one relatively common complication everyone has experienced but has rarely been addressed in the literature: necrosis of the mastectomy skin flap. Unless the integrity of the native chest wall skin can be predictably preserved, not only is the entire concept and advantage of SSM lost, but immediate breast reconstruction is threatened as well. Central to this problem is the thickness of the skin flaps and preservation of an appropriate amount of subcutaneous tissue that helps to insure flap viability. It would seem that there should be a balance between preservation of adequate flap thickness without compromise of oncologic principles.
Clinically, there appears to be a subcutaneous layer of tissue between the epithelial/dermal tissue of the breast and its parenchyma. If this layer can be identified and respected by the oncologic surgeon, the potential of a predictably viable flap that contains little or no breast tissue might be realized.
To address the feasibility of satisfying these two goals, we studied normal breast tissue removed in patients receiving reduction mammoplasty and the relationship between the breast tissue, the skin, and the intervening subcutaneous layer of tissue.
The breast specimens of women receiving reduction mammoplasty were examined histologically by an experienced, blinded breast pathologist. The distance from the most caudal border of dermis to the breast parenchyma was measured. This was then correlated with the patient’s age, BMI, and breast specimen weight. Due to the presence of repeated measures and censored data, survival analysis methodology was used. Specifically, a Cox proportional hazards regression with robust variance estimators was fitted using PROC PHREG in SAS 9.2.
In this IRB approved study, 76 specimens of 38 women were examined. The range of thickness of the subcutaneous layer between the dermis and the breast parenchyma was 0.0 cm to > 2.9 cm, with a median of 1.0 cm (95% Confidence Interval of 0.9-1.2 cm). There was no correlation of the thickness of the subcutaneous layer with age, BMI, or breast weight.
In almost all women in this study, there is a distinct layer of subcutaneous tissue between the dermis and breast parenchyma that is as thin as 3 mm and as thick as 3 cm (median 1.0 cm) that does not contain breast tissue. With this anatomic fact in mind, the oncologic surgeon may justifiably and safely consider preserving skin flaps of 1 cm or more, thereby insuring both oncologic safety and predictably viable mastectomy skin flaps.