Health A-Z

How Does Cancer Start?

Reading Time: 4 minutes

We’ve all heard the word ‘Cancer’ and the feeling of dread it carries along with it but ever wondered about the nitty-gritty details? How does it start? How does it grow? How does it spread from one part of the body to another?

Without a doubt, cancer is one of the biggest challenges in medicine globally. It has been for a while but the good news is that with the numerous research studies that have been done thus far, the science behind cancer is better understood (although not completely, but a lot of progress has been made). Thanks to cancer research, we now know how to prevent and manage certain types of cancer, and so it’s not always sad endings.

What is cancer?

Cancer is when for some reason, some cells in the body become abnormal, lose control and start dividing and growing unusually quickly. Normally, cells divide, grow, and die once they’re old or damaged, giving way for new cells to form. But cancer cells are abnormal in the sense that they are out of control and don’t die when they should, forming new cells when they are not needed. They just keep going….

How does cancer start?

Image adapted from Cancer Institute NSW 

Cancer begins at a cellular level i.e. within the cells of the body; could be one cell or a group of cells depending on the type of cancer. Under normal circumstances, our cells divide at intervals, which are regulated by special signals- one of the body’s control mechanisms. These signals tell the cells when to divide and how much dividing to do, ensuring just the right amount of cells are produced at the right time. If for any reason these special signals become defective or become MIA (missing in action), this causes the processes of cell division and growth to go into overdrive.

Image adapted from ACCR Foundation

They will basically divide and grow continuously at an abnormally fast rate, so much so that they form a mass, which is more appropriately referred to as a tumour. The exception would be in leukemia where the abnormal cells don’t form tumours; instead, they float around in the blood.

Video adapted from PatientEd Channel on Youtube

Every cell has a nucleus, which you can think of like a Control Tower at an airport. Within the nucleus are genes, which basically tell the cells what to do and how to do it using the special signals I mentioned earlier. Defects in the genes (mutations) are responsible for the malfunctioning or absolute disappearance of these special signals, which is the genesis of cancer.

Image adapted from Sukino blog 

Mutations can be either inherited or acquired. Smoking, including secondhand smoking, exposure to UV (ultraviolet) light or radiation, obesity, hormones, nitrosamine (chemical found in smoked foods), carcinogens (chemicals that cause cancer), viruses, chronic inflammation, etc. have been implicated with the capability of causing gene mutations which in turn can kick-start the cancer process. Although cells, along with the genes within them get damaged very often, there are mechanisms in place to repair the damages without problems. However, more serious damage or a build-up of relatively minor damages overtime could result in a mutation.

Image adapted from Total Assist UK 

How does cancer spread?

Cancer can be either benign or malignant. Benign cancers are milder forms of cancer that don’t spread beyond where they started. Malignant cancers behave more aggressively; they spread to other parts of the body. Cancer could spread via the blood, the lymph (clear fluid which contains white blood cells), or directly (to neighboring parts of the body). How and where cancer spreads to depends on its type and location. To spread, part of the rapidly dividing cells or tumour has to break off from its primary site and transport itself to a secondary location. This is called Metastasis. Once it arrives at its secondary location, it plants itself and begins the process of dividing and growing rapidly to form more cancer cells and tumours.

Image adapted from Teresa Winslow @

Image credits: Featured image-; Sukino-; Total Assist; Cancer Institute NSW; Teresa Winslow @

Dr Wendy Evans-Uhegbu

The author Dr Wendy Evans-Uhegbu

Dr. Wendy Evans-Uhegbu is a graduate of The Royal College of Surgeons in Ireland, with experience in Connected Health, Medical Technology, Clinical Research, Medical Education, Medical Communications, and Web Design/Development. She is a part of the Medics Abroad team with the role of Chief Communications Officer. She is also a Medical Writer at 3D4 Medical and runs a Medical Communications and Children's books company (ODR Integrated Services/ ODR Books).  She is the author of the newly published children's book series "The Things Around Me".

Leave a Response