Sentinel Node BiopsyMedical editor Ellen Schlichting MD
Oslo University Hospital
Sentinel node biopsy (SNB) is used in the treatment of early stage breast cancer. This procedure is usually performed concomitant with breast conserving surgery or mastectomy.
There is a primary lymph node (sentinel node) which drains the lymph from a certain area.This sentinel node reflects the status of the remaining lymph nodes because the sentinel node is the first node where malignant cells from the primary tumor will locate. If the sentinel node does not contain tumor cells, the other lymph nodes in the axilla will, with a high probability, be free of metastases, and axillary dissection is unnecessary*.
Two methods are used for identifying sentinel nodes: radioactivity and staining. The radioactive isotope, 99m Tc-labeled colloidal human albumin, is injected some hours, or possibly one day, preoperatively. Methylene blue is injected immediately preoperatively. Lymphoscintigraphy is done after injection of radioactive isotope.
By this procedure, blue and/or radioactive lymph nodes are excised, and sent for histological examination or as frozen sections. Sentinel lymph nodes should have activity over 5 and preferably > 10x background activity.
- Invasive carcinoma stage T1 -T3 without evidence of lymph node metastasis.
- DCIS van Nuys grade 3 histologic where mastectomy will be performed. An axillary dissection should not be performed in this situation if the sentinel node is not found.
- If breast conserving surgery for DCIS is to be performed, SNB is not indicated. However, if the final diagnosis is invasive carcinoma, the SNB can be done afterwards.
- Avoid unnecessary axillary dissection
- Avoid destruction of lymph drainage of the arm
* Kim T et al. Lymphatic mapping and sentinel node biopsy in early stage breast carcinoma. Cancer 2006; 4-16
Tc-labeled colloid human albumin
There are no special preparations for the injection of 99m Tc-labeled colloidal human albumin.
The line of the incision is drawn on the skin with the patient upright.
The operation is performed under general anesthesia.
The patient lies in the supine position.
The ipsilateral arm is positioned at an angle of 70-90 degrees from the body.
- 99m Tc-labelled colloidal human albumin is injected peritumorally at the department of nuclear medicine.
- While images are taken, the patient lies on her back with the arm over her head.
- The first images are taken immediately after the injection.
- New images are taken after 30 minutes.
- As needed, images are taken after 4 hours.
- The position of the sentinel lymph node is marked on the skin, from the front and side.
A gamma detector is used during the operation, which registers the radioactivity. Methylene blue is used simultaneously to increase the detection rate of the sentinel lymph node.
- Methylene blue is injected peritumorally at the beginning of the operation.
- An incision is made in the skin according to preoperative drawing.
- The sentinel lymph node is identified with the aid of the gamma detector.
- The sentinel lymph node is removed.
- The lymph node is verified with the gamma detector, and if there are several, they are also removed.
- The lymph node is sent for histological examination.
With a negative frozen section, an axillary dissection in not performed. Immunohistochemical tests are then awaited from the pathologist, which usually take about one week.
If there is evidence of cancer cells, an axillary dissection is performed. This occurs in 5% of cases.
In the event the surgeon does not find the sentinel lymph node, an axillary dissection must be performed.
The procedure is followed by breast conservative treatment or mastectomy.
Allergic reactions to human albumin can occur.