Sentinel node detection in breast cancer surgery

As is evident from several studies and reports, breast cancer incidence is on the rise and we are also seeing it occurring in younger people. Approaches aimed at early detection of this cancer have gained prominence with the thrust toward breast conservation surgery.

This means that if the cancer is picked up early and the lump is still relatively small, only the affected portion of the breast is removed through a technique known as lumpectomy.

This breast-conserving surgery is a relatively recent development and has been validated by several studies making it an accepted practice in many parts of the world.

Further exciting development has been the use of minimal surgery, which saves many patients from unnecessary removal of lymph nodes in the axilla, a procedure that often leads to swelling of the arm due to disruption of lymphatic drainage.

These lymph nodes are removed because breast cancer usually spreads to them first through the lymphatic channels.

Initially, the cancer cells will be present in only microscopic quantities, but later these cancer deposits grow in size, thus enlarging the glands and making them palpable on examination. This means that cancer has spread to these glands and they, therefore, need to be removed.

In the past, if the nodes were not palpable or enlarged, they were still routinely removed to rule out the presence of microscopic spread of cancer in these patients, leading to many cases of swelling and pain in the affected arm.

However, on pathology examination, many of these patients turned out not to have any tumour cells spread to these nodes and the surgery was therefore unnecessary.

All this has changed with the availability of a new technique to detect cancer spread to these nodes. Using the nuclear medicine services available at the Aga Khan University Hospital, Nairobi, a small amount of a radioactive colloid is injected into the breast.

This colloid passes through the lymphatic channels towards the nodes in the axilla until it finally reaches a node.

This node, which receives the lymph drainage directly from the breast, is known as the sentinel node (gatekeeper node). The procedure is done using a gamma probe in the operating theatre. The probe detects the radiation from the radioactive colloid in the sentinel node, and thus leads the surgeon in detecting and dissecting out the node.

The importance of detecting this sentinel node is based on the understanding that if the cancer cells were to spread to the nodes in the axilla, they would end up initially in this sentinel node before spreading to the other nodes.

Identifying this node, removing it and sending it for pathologic examination under a microscope would show if the cancer has spread to the sentinel node.

If the cancer has not spread to this node, then it can be safely assumed that it would not have gone beyond it to any of the other nodes in the axilla, making the dissection of the other nodes unnecessary, and in effect saving the patient from an unnecessary axillary nodal dissection.

This technique has become the standard practice in patients whose breast cancer is detected early, and along with breast conservation surgery, constitutes significant progress in the concept of minimally invasive and optimised surgery.

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