Here’s a very simple analogy:
Imagine yourself as a tumour cell- You started off alone and now after multiplying, you’ve had to live with your ever growing family(the Primary Tumor Mass), and now there just isn’t enough food and glucose for everyone to live off.
The roads of arterial supply that get you your nutrients have been exploited too far.
So one day, you get kicked off from the main tumor mass to make room for the younger tumor cells.
Once you’re separated away from mama tumor, you’ll now need to find a new place to settle.
Breast tumor cells love to ride through a system of vessels in your body known as the lymph vessels. These lymph vessels are filtering systems(for bacteria, etc.) that have watchposts periodically called “nodes” and they eventually carry the excess blood that has naturally “leaked out” from veins back to the heart.
Tumor cells are smart enough to use this system to “travel” when looking for a new place to seed.
Here are the paths most little breast tumor outcast cells use to “spread” and create Secondary Tumors:
- If in case the tumour is in the medial aspect of the breast, they’ll move towards the closest (lymph) nodal group or the internal mammary lymph nodes, or into the contralateral breast.
What this means in simpler terms is that if you had a lump in the center of your chest, it’s more likely to spread to the closest Lymph Node checkpoint it can find or into your other breast directly- because that’s how the lymph vessels run in the body.
- If it is in the lateral aspect of the breast you move towards the axillary lymph nodes.
In other words, if you have a tumor closer to your chest border, it’s more likely to spread into your armpit(axilla).
- If it is in the posterior(behind) aspect of the breast you move towards the posterior group of lymph nodes.
- If it’s in the lower quadrant(inferomedial quadrant) of the breast, you move towards the subdiaphragmatic lymph nodes and further through the caval opening to invade the abdominal organs.
This means that if the tumor was in the lower-central area of the breast, it’d travel downwards and under your diaphragm and enter right into your tummy.
- A Tumor cell may also dislodge from the primary site and enter the internal thoracic veins- These are vessels which carry spent blood from the chest wall and breast back to the heart.
Unfortunately, these vessels also have connections with your spinal bones(called vertebrae) through a venous vessel system known as the “vertebral plexus”.
This for a tumor cell is like joining the Highway:
Once a tumor cell enters this vertebral plexus system, it’s got free flow access to go to the pelvis and even the brain, tracking along your vertebral column.
- Finally, If the tumour is in the upper part of breast, it could move towards the apical nodes to the supraclavicular nodes and then on to cervical group of lymph nodes, and further beyond to parotid lymph nodes.
In essence, the tumor in the upper breast can go through your collar bone lymph vessels, into your neck, and even reach your salivary gland called the parotid.
We’ll be discussing Mets further under their respective sub-articles.