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Sentinel node biopsy is a procedure to determine whether breast cancer cells have spread beyond the breast tissue. By injecting a blue dye or radioactive tracer (or both) into the breast, the surgeon can follow the lymph system from the tumor to the sentinel node, the first underarm node most likely to contain cancer cells if they have spread beyond the breast. Sentinel node biopsies are performed when invasive breast cancer is diagnosed. If the sentinel node is found to be clear of cancerous cells, a woman is spared the more conventional “axillary dissection,” a more invasive surgery to remove many of the underarm lymph nodes. Axillary dissection can cause “lymphedema,” an uncomfortable, long-term complication caused by fluid build-up in the arm.
Risk-reducing mastectomy does not typically include either sentinel node biopsy or axillary dissection because the woman is assumed to be free of breast cancer. However, because breast cancer is found in a small percentage of high-risk women during risk-reducing mastectomy, some breast surgeons perform sentinel node biopsy as a precautionary measure, to spare women the more extensive axillary dissection if cancer is found. If invasive breast cancer is found during risk-reducing mastectomy, the surgeon samples underarm lymph nodes to see if the disease has spread, and to determine appropriate treatment.
One small study looked at sentinel node biopsy in 143 women who had risk-reducing mastectomies. In this study, four women had invasive cancer found at the time of the risk-reducing mastectomy: two had positive sentinel nodes, while two had negative sentinel nodes. The two women who had a negative sentinel node biopsy at the time of their mastectomy were able to avoid further axillary dissection. Women considering risk-reducing mastectomy should discuss the benefits, risks and limitations of sentinel node biopsy with their surgical team.