Links to other sub topics in this section:
Links to other sub topics in this section:
A cancer, anywhere in the body, spreads by three routes; by local extension, by lymph nodes, and by blood.
All organs in the body have their unique lymphatic drainage. Blood flows from heart to the big arteries to small arteries to very minute capillaries to small veins to large veins and back to heart. As the blood flows from a larger sized vessel to a progressively smaller sized vessel, because of pressure, some fluid from the vessel gets filtered out. This fluid is collected by tiny 'lymphatics' which successively unite to form larger sized lymphatics, and which ultimately drain into 'lymph nodes' stationed in axilla in case of breast. (There are other nodal stations also for breast, but I wont go into details and make it complicated).
So, naturally, once a cancer forms in the breast, it keeps on enlarging, and ultimately breaks into this lymphatic system, and it may spread to these nodes in axilla via this lymphatic system. This can happen fairly early in the disease, with even smaller sized tumours (1 or 2 cm in size), having almost 10% to 20% chances of having a lymphatic spread. As the size increases further, the chances of lymph node involvement increases much more. So if we dont remove these nodes, disease will remain behind, and will come back very soon.
Because of this lymphatic spread, an Axillary Lymph Node Dissection (ALND) is a very important component of all breast cancer surgeries. In an ALND, all the fibro fatty lymphatic tissue in the axilla is removed.
Yes, all patients with breast cancer will need ALND to achieve a complete clearance of the axilla. If, on clinical examination of the patient, the nodes are enlarged, ALND is a must. For those patients who have small tumours, and no palpable nodes, the concept of 'Sentinel Lymph Node Biopsy' has come into being.
We have understood three main things:
Arm swelling after ALND If you have read the first question above, you will ask 'If the lymph nodes are removed, what happens to the lymphatic fluid which is filtered in the arm; how does it return back?'. Well, most patients who have undergone an ALND will have some degree of swelling of the arm of the same side. In a few, this swelling will be massive, almost double the size of the other arm, or even more. This is a very dreadful complication of ALND, and there is nothing much we can really do about it?
Systematic involvement of lymph nodes by cancer The lymph nodes in axilla have been given levels (3 levels actually). Over the last few decades, it has been realized that the lymph flow from the breast, in the vast majority of patients, follows a systematic flow from level 1 in lower axilla to level 2 in upper axilla to level 3 high up in the apex. Only in a very very few patients will the lymph flow directly to level 3 node, bypassing the levels 1 and 2. This is a very significant understanding.
Stage wise lymph node involvement As the stage of a breast cancer increases, chances of lymph node spread also increase. So in early stages, the lymph node involvement may ne much less; for example, in stage 1, only 1 lady out of 5 (20%) may have lymph node involvement. But all will undergo an ALND. So cant somehow avoid an unnecessary ALND in those 4 ladies?
Reading the answer to the above question, it makes sense that if we were to identify the nodes in lower axilla (level 1), where the lymph drainage occurs first, test them (by pathology, frozen section) intra operatively for presence of any disease; and if there is no disease in those nodes, then the chances of disease being above will be very less, and we could avoid a complete axillary lymph node dissection in such patients, thereby decreasing the side effects of an ALND.
So the principle of a Sentinel Lymph Node Biopsy (SLNB) is to identify the first level draining nodes during the surgery, and testing them for presence of disease. If these nodes are positive for disease, we do a complete axillary lymph node dissection. If these nodes are negative for disease, then we avoid an axillary lymph node dissection.
Only those patients who are 'clinically' node negative (patients in whom there are no palpable enlarged lymph nodes), must be offered a SLNB. Those patients, who have palpable nodes (palpable means one can feel the nodes by inserting fingers in the axilla), MUST undergo a complete axillary lymph node dissection.
This answer with details will be up soon.