Cancer is the term given to a class of diseases characterized by an abnormal division of faulty cells manipulated by DNA mutations (some sort of a disturbance in one or more of the above-mentioned gene types), in an overrated manner which eventually invade the surrounding tissues and disrupt their normal functional capabilities. Malignant transformation is a complicated process by which healthy cells gradually convert into cancerous cells in the body.
Read more: How Do Cancer Cells Develop.
How Do Cancer Cells Spread
When cancer cells increase in number and size, there will be no room for them to stay localized in the initial plot and as a result, they will start spreading all over the body because there will be enough oxygen and nutrients for them to function effectively.
Cancer cells always choose the path which is least resistant; therefore, blood vessels with harder walls and organs with thick basement membranes will be safe. The commonest modes of distribution include local invasion, via bloodstream (circulating tumor cells) and lymphatic spread.
Bloodstream Spread
Cancer cells entering the bloodstream are known as circulating tumor cells. They get lodged particularly in capillaries and sometimes diffuse to a nearby organ. These cells will be able to divide effectively in the invaded organ as long as the oxygen and nutrition supply is adequate. Sometimes they will fight with body cells for these factors and win, causing the intrinsic tissues to die.
However, these go through a very complicated journey by sweeping through tiny blood vessels, so a small percentage of cancer cells will end up reaching the destination whereas others will die. However, effectively functioning cells will somehow spread from one place to another and give rise to secondary tumors-Metastasis.
Lymph Node Spread
This is a system of interconnecting tubes which has a responsibility in maintaining body’s defense mechanisms. Cancer cells, which first invade tiny lymph vessels will slowly spread from one tube to another, spreading throughout the system. Some cells will die on the way whereas majority will be able to resist and divide rapidly to form a proper tumor which will spread to nearby structures as well.
Local Invasion
In this process, cancer cells which have already invaded certain organs through blood stream will invade other nearby structures by direct implantation or seeding.
E.g From prostate gland to liver to lungs
Image Courtesy:
“Diagram showing gallbladder cancer cells in the nearby lymph nodes CRUK 438” By Cancer Research UK uploader – Own work (CC BY-SA 4.0) via Commons Wikimedia
“Diagram showing cancer cells spreading into the blood stream CRUK 448” By Cancer Research UK uploader – Own work (CC BY-SA 4.0) via Commons Wikimedia
