Pathology and resection margins following mastectomy prior to immediate breast reconstruction

Risk of local recurrence (LR) (and even distant disease-free survival) after mastectomy is associated with margin status. Furthermore, the vast majority of LR are located at the anterior (superficial) margin. Margins in mastectomy are considered anatomical borders and not true resection margins; such a conception may erroneously lead to underestimation of the risk of LR after mastectomy. If dissection is accurate along the fascia, only skin, subcutaneous tissue and minimal residual breast gland tissue (rBGT) are expected to remain in the patient. However, the subcutaneous fascia is an inconsistent anatomical structure that may be absent in almost half of patients. Studies and routine clinical practice suggest that resection may frequently, though often focally, be within the breast glandular tissue leaving various amounts of rBGT. Such areas may be nidus for subsequent de novo or recurrent premalignant or malignant disease. There is no consensus on handling of close/positive margins and intervention is extrapolated from studies on breast conserving surgery with subsequent radiotherapy. Handling of a close/positive margin is complicated by poor correlation between the ex vivo findings on the specimen and the attempt to relocate the area of concern in a patient with reconstructed breasts. In this clinical practice review, we strongly advocate for reporting of the lesion-to-margin distance in mastectomies to collect further evidence on the association between LR and margin status.