How Cancer Cells Start, Develop into Tumors, and Spread
Key takeaways:
Cancer begins when a group of cells have a change in their DNA that allows them to divide uncontrollably.
When cancerous cells develop and replicate, they can organize into a growth called a tumor.
Sometimes cells can break free from a tumor and establish new tumors in other parts of the body.
The mutations that lead to a cancer cell can occur because of an inherited gene or an environmental exposure that mutated the cell’s DNA. Most likely it’s a mix of both.
A cancer diagnosis often feels scary and overwhelming. And after the diagnosis, doctor appointments and treatment plans can be even more difficult to understand and process. Cancer is a complicated disease with confusing terms to describe types of cancers, stages of disease, and treatments. This article will explain the basics of cancer, and it’ll provide you with a helpful framework so you better understand all the different parts of your cancer care. Understanding these fundamental concepts can often alleviate the natural feelings of anxiety and uncertainty that come with the diagnosis.
Defining cancer terms
Before explaining how cancer starts, let’s define some of the terms that are used when describing the disease. The glossary of cancer-related terms is long. But learning a few commonly used words will help you understand medical discussions as you or a loved one moves through the diagnostic and treatment process.
Cancer: A disease in which a group of cells have a change in their DNA that allows them to divide and replicate at a faster rate than normal cells.
Tumor: A solid growth made of mutant cells. Tumors can be benign (noncancerous) or malignant (cancerous).
Benign: A benign tumor contains cells that aren’t cancerous. This means that they don’t have the ability to invade surrounding tissues or spread to other, distant areas of the body.
Malignant: This is another word for cancerous. A malignant tumor contains cells that have the ability to invade surrounding tissues. These cells can even travel (metastasize) to distant areas of the body and establish new tumors.
Metastasis: This is the process by which cancer cells spread. A cancerous cell in a malignant tumor can break away and travel to another part of the body, where it can establish a new tumor. The word “metastasis” refers to this process, but it can also describe the new (metastatic) tumor itself. A metastatic tumor is often referred to as a “met.”
How does cancer start?
There are trillions of cells in our body. And they all follow a similar life cycle that allows them to reproduce. A cell’s DNA programs it to replicate and make new healthy cells. In addition, a cell’s DNA programs a cell to die when it becomes damaged or is no longer functional.
Sometimes a cell’s DNA gets damaged or copied incorrectly when the cell is replicating. This is called a mutation. The cell cycle has built-in checkpoints to identify these mutant cells, and then destroy them. But occasionally these mutations give the cell a survival advantage, allowing it to get past these checkpoints. The result is that the mutant cells grow at an abnormal rate, which leads to more cells with the altered DNA that can replicate abnormally.
In the same way a mutation in a virus may make it more resistant to a treatment, a mutation in a cell may give it a superpower that allows it to dodge the normal mechanisms that are designed to keep it in check.
From cancer cell to tumor
When a group of cells outsmarts the system of checks and balances, they replicate uncontrollably. As the number of cells grows, they can form a tumor. And if a cancerous tumor grows undetected for a long period of time, it can start to invade the surrounding areas of the body. In other words, what started as a small and contained town becomes a thriving and busy city that expands into surrounding suburbs.
From tumor to metastasis
Similar to the way some people move away from a crowded city to another less populated area, cancer cells can hitch a ride through the bloodstream or lymphatic system and travel to distant parts of the body. This is how metastatic cancer starts. And while those traveling cells don’t always survive the journey or successfully set up camp in a new location, sometimes they start to grow into a new tumor. For example, a breast cancer cell can grow a new cancerous tumor in the liver.
What causes DNA mutations in the first place?
If cancer begins with a mutated cell, you may be wondering what causes the mutation in the first place. Like many other diseases, this is a combination of genetics and the things we are exposed to in our environments.
Many diseases and cancers are linked to inherited genes. These genes can make us more susceptible to certain physiologic changes in our bodies that lead to these conditions. The BRCA gene is one of the most common examples in cancer. When it functions normally, this gene helps to repair damaged DNA and prevents the mutations we discussed earlier. But if someone inherits one of two altered versions of that gene (referred to as BRCA1 and BRCA2), the gene is less protective. This makes it more likely that they will develop breast cancer.
But inherited genes aren’t the full story. We are exposed to things every day that have the potential to damage our DNA. These are sometimes referred to as “carcinogens.” Some well-known examples are:
Ultraviolet rays from the sun
Chemicals in cigarettes
Asbestos
Radioactive chemicals
As we learned earlier, our body is well equipped to protect us from damaged DNA before it becomes a problem. But the more we’re exposed to these carcinogens, the more opportunities these mutations have to escape the watchful eye of the protective cellular mechanisms. This is why the more sunburns someone has over their lifetime, the more they increase their risk of skin cancer.
But there’s no magic formula for determining why some people develop cancer while others don’t. A healthy young woman with no family history or genetic risk for cancer may develop a breast tumor in her 30s. And someone who sunbathes and smokes cigarettes every day may never develop an identifiable cancer. We still have a lot to learn. In the meantime, still try to avoid cigarettes and sunburns.
The bottom line
DNA mutations and errors in cell replication happen in our body every day. And our body is pretty good at protecting us from these mutated cells before they ever become a problem. When a mutation slips through the cracks, it has the potential to multiply and organize into a tumor. And cells from that tumor can also travel to other areas of the body and make new tumors. But if this happens, experts have developed an arsenal of treatments to kill the cancerous cells in the tumor itself, along with any wandering cells that may have escaped.
Why trust our experts?
References
American Cancer Society. (2021). Breast cancer risk factors you cannot change.
National Cancer Institute. (2018). Cancer-causing substances in the environment.
National Human Genome Research Institute. (n.d.). Mutation.
