Author: Jeffrey Boschman, MSc in Biomedical Engineering, Artificial Intelligence in Medicine (AIM) Lab at the University of British Columbia
Edited by: Celine Laumont, Alex Lukey, Ariadne Holness de Hiller (Patient Partner), Siv Klausen (Patient Partner
Introduction
When hearing the word “tumour”, many people think about “cancer” and use these two terms interchangeably. A lot of our current medical terminology about cancer comes from descriptions of tumours made more than 2000 years ago. The Greek physician Hippocrates was the first to describe tumours using the words “carcinos” and “carcinoma” (Greek word for “crab”), that turned into the word “cancer”. Later, another ancient physician named Galen described tumours using the word “oncos” (Greek for “swelling”), giving rise to today’s “oncologists” or “oncology”. Although enlightening, the history of terminology can be misleading because we now know that not all tumours are cancerous and not all cancers form tumours. Simply put, cancer is a disease where some of the cells of your body lose the ability to control how quickly they should replicate.
In this article, we will discuss the basics of what cancer is and how it starts.
Basics of Cells
The human body is made up of trillions of cells. There are many types of cells: skin cells, lung tissue cells, red blood cells, and white blood cells are just a few examples. All of these cell types perform specific functions and regularly interact with each other to keep the body’s systems working. Normally, cells can regulate themselves – only reproducing when they need to replace cells around them or when the body is growing. When a normal cell gets old or damaged, it triggers apoptosis, or programmed cell death, to get removed from the body.
As opposed to normal cells, cancer cells have lost the ability to regulate themselves. As such, cancer cells can either divide too quickly, avoid programmed cell death, or both.
How Cancer Starts
The biological process that controls the behaviour of cells is located in the cell’s DNA. Although all the cells in someone’s body have the same DNA, different cell types are able to perform specific functions because they activate different sections of this DNA (genes).
When a cell divides, it first copies its DNA and then splits into two cells, each with a copy of the original cell’s DNA. However, not all copies are perfect, and mistakes, so-called mutations, are often introduced during the copying process. Certain harmful substances, like chemicals in cigarettes or ultraviolet radiation from the sun, can also favour the introduction of mutations in the DNA . Most mistakes are fixed right away by gene products specializing in DNA repair or tumour suppressor genes. As a last resort, white blood cells (part of the body’s defence system) should find and kill mutated cells escaping this DNA repair system.
Sometimes, cells bearing harmful mutations go undetected. As a result, they can keep dividing and create more cells bearing the same harmful mutations in their DNA. These new cells divide and create even more of these mutated cells, continuing the cycle and leading to the accumulation of cancer cells in the body until it becomes detectable by clinical tests.
Benign vs. Malignant
Tumours are clumps of cells that have grown in a place they aren’t supposed to. However, as mentioned before, not all tumours are cancerous. A benign tumour is an abnormal clump of cells that (1) does not grow or grows very slowly, (2) does not invade surrounding tissues, and (3) does not spread around the body. Conversely, malignant (or cancerous) tumours tend to grow quickly, invade neighbouring tissues, and spread around the body. Again, it should be noted that not all cancers form solid tumours – leukemia, for example, is a white blood cell cancer which does not form tumours. There are also cases where specific types of benign tumours may later become malignant, thereby requiring close monitoring by a medical professional.
Cancers Staging and Metastasis
Most cancers are named after the organ where they start in the body. For example, if lung cancer spreads to the liver, it will be considered as a lung cancer with a secondary tumour in the liver. To be more specific, medical professionals also talk about the stage or the grade of a cancer. Cancer staging often includes information about the cancer size and location, the specific cell type involved (carcinoma, sarcoma, leukemia, lymphoma, etc.), and whether or not the cancer has spread to other areas of the body. When cancer travels around the body to other locations (through either the bloodstream or the lymphatic system, or just by going to the surrounding tissues/organs), this is called metastasis. Cancer grading involves information about how different cancer cells are from normal cells.
Cancer is Not a Single Disease
A final thing to point out is that “cancer” is not just one disease. Many different mutations in DNA can cause cells to divide uncontrollably, resulting in one of the many diseases that are called “cancer”. These mutations, as well as other factors including cancer location and spread, make some cancers harder to treat than others.
The Future of Cancer
Approximately 167 billion US dollars was spent on cancer research globally in 2020. Every year, scientists learn more and more about cancer and develop new strategies to prevent cancer and innovative technologies to improve treatment for patients. The future is filled with hope.
Sources
https://www.cancer.org/cancer/cancer-basics/history-of-cancer/what-is-cancer.html
https://jamanetwork.com/journals/jamaoncology/fullarticle/2768634
https://www.cancer.gov/about-cancer/diagnosis-staging/staging
https://cancer.ca/en/cancer-information/what-is-cancer/stage-and-grade
https://www.statista.com/statistics/696208/oncology-costs-worldwide/