What Happens During the Sentinel Node Biopsy Procedure?
Sentinel node biopsy is usually performed at the same time that a lumpectomy is performed. If this is the case, the sentinel node biopsy is usually performed first.
Depending on the preference of the doctor, the blue dye or radioactive tracer may be injected after the woman has received anesthesia. The surgeon then uses a handheld Geiger counter to determine the exact location of the sentinel lymph node and makes a small incision over that point. If the patient has been injected with blue dye, the sentinel lymph node is colored blue. This provides the surgeon with visual confirmation of the sentinel node.
The surgeon then removes an average of two to three sentinel lymph nodes for examination under a microscope. Depending on the surgeon's practice and suspicion, a pathologist may do a quick test after freezing the material (known as a frozen section) to examine these nodes for cancer while the surgeon performs the lumpectomy or the mastectomy. If cancer cells are found in the sentinel lymph node, either at the time of surgery or when the final report from the pathologist is available, the surgeon then performs an axillary lymph node dissection.
A sentinel node biopsy typically takes about 45 minutes to perform. If a lumpectomy is also being performed, an extra 30-45 minutes are usually added to the total surgery time.
For melanoma, the basics of the procedure are the same. However, not all patients with melanoma require a sentinel lymph node biopsy. If lymph nodes are palpable during a physical examination a sentinel lymph node biopsy is mandatory. For most patients a melanoma less than 1 mm thick does not require a sentinel lymph node biopsy, unless ulceration of the melanoma is present. For tumors 1-4 mm thick, the incidence of lymph node spread increases as the thickness increases. Therefore, sentinel lymph node biopsy of the draining basins are carried out. If there is a positive sentinel lymph node, a complete regional lymphadenectomy (removal of all of the draining lymph nodes) is performed. This is standard of care. However, this procedure has not been demonstrated to improve survival of patients with melanoma.
For patients with deep melanoma, sentinel lymph node biopsy alone is sufficient due to the severe side effects of lymphadenectomy. The sentinel node biopsy is helpful, however, in guiding diagnostic, prognostic and therapeutic decision making.
Persons with melanoma, who have a positive sentinel lymph node, may benefit from additional therapy such as radiation, interferon, interleukin, or, based upon new information, the drugs ipilimumab (Yervoy), nivolumab (Opdivo), or pembrolizumab (Keytruda) may be considered.