The surgeon then uses a hand held counter to detect the radioactive tracer and locate the sentinel node. Since the uptake of the technetium-99 by cancerous lymph nodes is sometimes different than the uptake by normal lymph nodes, these nuclear medicine images may also help show which lymph nodes are cancerous. Depending on the protocol followed, the surgeon usually waits between 45 minutes to 8 hours after injection before bringing a patient to the operating room for the biopsy. At some point during the procedure, a small amount of blue dye will also be injected into the breast tissue near the area of the tumor. The blue dye provides additional visual confirmation of the sentinel node's location during surgical removal.
Most patients have only one to three sentinel lymph nodes under the arm.
Thus, an average of only two lymph nodes are removed in each patient with a sentinel node biopsy. This, in turn, may reduce post-operative complications. A standard axillary node dissection , removal of the underarm lymph nodes, usually requires a larger four to six inch incision and a longer recovery period than a sentinel node biopsy. Researchers are currently investigating whether sentinel node biopsy should routinely be performed in place of axillary node dissection. However, surgeons caution that more studies on the benefits and risks of sentinel node biopsy should be conducted before the procedure becomes widespread.