PETER CHIN
SENTINEL NODE BIOPSY/
NODE DISSECTION
WHAT IS SENTINEL NODE BIOPSY?
Sentinel Node Biopsy is a procedure commonly performed as part of the management of breast cancer and melanoma. The Sentinel node is the first lymph node which receives drainage from lymphatics within a specific region. By removing the sentinel node, one can determine whether cancer cells have spread to the node itself. This will help with predicting long term outcome and will guide further management.
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HOW IS IT DONE?
The sentinel node can be located by injecting radioisotope near or adjacent to the tumour site prior to surgery. Thereafter, a lymphoscintiscan is often performed to map out the site(s) and number of sentinel nodes. Blue dye may also be injected during surgery to assist with sentinel node identification.
In the context of breast cancer, sentinel nodes are usually in the axilla (armpit).
For melanoma, the sentinel node may be located in the neck, above the clavicle (collar bone), axilla or groin, depending on the site of the initial lesion and the lymphatic drainage.
The sentinel node is then removed and sent to the laboratory for microscopic analysis to check on whether there are tumour cells present.
Finding the true sentinel node(s) can be difficult, but is important so that an accurate picture of the cancer can be obtained. The sentinel node biopsy operation will have the highest chance of success if performed by a surgeon who is specifically trained in the technique and regularly performs the procedure.
WHAT IF CANCER IS FOUND IN THE SENTINEL NODE?
If a sentinel node contains tumour cells, the treatment options are radiotherapy (breast cancer), or further surgery (breast or melanoma) to remove the rest of the lymph nodes in the area to ensure that any tumour cells remaining are removed too. This operation is variably known as Nodal Dissection or Clearance, Block Dissection, Neck Dissection, Axillary Dissection or Axillary Clearance and Groin Dissection, depending on the location of lymph nodes.
The surgery is performed with meticulous attention to ensure that the nodes and lymphatics are completely and cleanly removed (“en-bloc resection”), so that there is no tumour spillage into surrounding tissue.
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AFTER THE OPERATION:
A drain is inserted after a nodal dissection to drain seroma fluid which is naturally produced by the body and secreted into the tissue space. This drain is removed once drainage slows down (up to 1–2 weeks after surgery, sometimes longer).
After the drain is removed, it is not uncommon for the body to continue to produce seroma fluid in this location. This is usually reabsorbed over time, but if a large volume is produced, it may result in visible swelling that becomes uncomfortable. This usually requires needle aspiration repeated as often as necessary.