Cancer cells under a microscope
Cancer cells can be found when errors occur in cell production.

Understanding Cancer Cells

Approximately 1 billion cells in our bodies divide every day. That is a tremendous amount of perfection required to ensure that cells are recreated to function properly. Errors can occur in some of those divisions which result in cell mutations, and these mutations can become cancer cells.

What Are Cancer Cells?

Normal cells construct our tissues and organs; they’re designed to grow and divide to create new cells on an as-needed basis by the body. When cells divide, they make exact copies of themselves, enabling the new cell to carry on the specific job of that particular cell type. Each cell in the body has a function and a purpose to maintain operations.

Cancer cells are created from mutations in these normal cells that prevent the body from functioning the way it should. These mutations aren’t the result of one cell changing one time; it’s a gradual transition from a normal cell, to altered cell, to cancer cell mutation. Not all cancer cells behave in an identical fashion, and how they act may depend on their stage in the mutation process.

Once they become cancer cells, they can remain localized in one area of the body, or spread from the primary cancer site throughout the body to other healthy tissues and organs.

Cancer Cell Formation

It’s difficult for a normal cell to become a cancer cell. It needs to be abnormal in ways that encourage growth, prevent cell repair and death, and ignore signals from the body.

When there is a change to our DNA, gene mutations are the result. These mutations mean that cells that should be resting divide at the wrong time and grow out of control, which leads to the creation of cancer cells.

Damage in DNA can be inherited in our genes. They can develop over time as genes wear out, or they can develop from other forces that cause damage to our genes, such as ultraviolet radiation or inhaling cigarette smoke.


How Tumors Are Created

When normal cells get old or have been damaged, they die off and are replaced by new cells. This normal process changes when cancer is in the picture: old and damaged cells don’t die off as they should, and new cells start to form when they’re not needed.

The result is a crowding of unnecessary cells which inhibit the function of normal cells. This is especially problematic because the surplus of cells keeps dividing without stopping, eventually causing tumors to form.

Cancers are usually classified based on where the abnormal cell growth began, such as liver cancer, lung cancer, etc. If the cancer metastasizes (spreads) to other parts of the body and creates a secondary tumor site, it would still be referred to as cancer of the primary origin.

What Are Tumors?

Tumors are abnormal growths of tissue that can be either benign or malignant.

Malignant tumors can spread into nearby tissues, destroy these surrounding tissues, and cause other tumors to develop. As they grow, some of the cancer cells can break off and go to other places in the body to form new tumors in different sites. Many tumors can be removed by surgeons, but malignant tumors can grow back in the future.

While malignant tumors may be life-threatening, benign tumors are not usually life-threatening. However, you should still watch them and have a doctor check them periodically.

Benign tumors can be large, but they do not spread. Unlike malignant tumors, benign tumors don’t typically grow back after they have been surgically removed.

For cancer of the blood, such as leukemia, solid tumors do not typically form. The blood can, however, transport cancer cells from one part of the body to another, and tumors can form at the secondary cancer site as well.

Types of Cancer Cells

There are as many types of cancer cells as there are types of cancer, which is in the hundreds. Some of the main types of cancer cells are:

  • Carcinoma Cells: these are cancers that start in epithelial cells that line body cavities. The vast majority of cancers are
    carcinomas.
  • Sarcoma cells: cancer cells that start in the connective tissues of bones, muscles, blood vessels, cartilage, and other tissues.
  • Leukemia cells: cancer cells that are found in the bone marrow.
  • Lymphoma and Myeloma cells: cancer cells that start in the immune system.

Leukemia, lymphoma, and myeloma cells are blood-related cancers and are fed by both nutrients in the bloodstream and lymph fluid.

Cancer Cells vs Normal Cells

Think of your normal cells as well-trained soldiers: they perform their duties to a high standard, listen to orders, and perform in their area of specialty. Cancer cells are soldiers that have gone rogue. Some of the largest differences in cancer cells are:

  • Cancer cells are able to ignore signals from the body. This enables them to keep multiplying or disregard orders to initiate apoptosis (cell death), which is how the body typically rids itself of old or damaged cells. Cancer cells have immortality, where normal cells have a shelf life. Cancer cells continue to reproduce even when further cells aren’t needed.
  • Cancer cells are less specialized than normal cells. Normal cells mature to form cells that assist in specific functions. Since cancer cells don’t serve a specific function, they can continue to divide without stopping. This out-of-control growth increases the number of the cancer cells and they begin to invade the surrounding normal cells.
  • Cancer cells can influence normal cells, molecules, and blood vessels in the vicinity of their presence. This is called a micro-environment; the cancer cells can get normal blood cells to feed a tumor with oxygen and nutrients, which helps the tumor grow. Cancer cells can also coerce blood vessels to remove waste products from the tumors.
  • Cancer cells can spread (metastasize) to other regions of the body. Normal cells make adhesion molecules, which cause them to
    stick to nearby cells. Cancer cells lack this sticky quality which lets them break free and go elsewhere. Without adhesion, cancer cells are able to grow into and damage the surrounding tissues and organs.

How a Normal Cell Becomes a Cancer Cell

Cancer cells are the result after a series of mutations, not just one single mutation. This may explain why cancer is more common in older people, as they’ve had a longer time to develop cell mutations.

The creation of cancer cells is often the result of several factors that work together to cause cancer. The change starts after normal cells mutate and become more abnormal in appearance.

There are two different types of mutations. Driver mutations result in the growth of cancer cells. Other mutations are called passenger mutations. Mutations can be inherited through our DNA or caused by carcinogens in our environment. Cancer cells don’t remain the same but continue to mutate throughout their lifespan.

This is why resistance in chemotherapy and targeted therapy drugs can build up over time. The new mutations in the cancer cells allow the damaging effects of these treatments to bypass the cells.

Cell Changes Between Normal Cells and Cancer Cells

A few stages on the spectrum between normal and cancer cells are hyperplasia and dysplasia.

With hyperplasia, there is an increase in the number of cells in an organ or tissue. Under a microscope, these will appear to be normal cells, just more of them than usual.

With dysplasia, these cells will look irregular, but they will have not yet become cancer cells.

Oncogenes and Tumor Suppressor Genes

Mutations in both oncogenes and tumor suppressor genes are found in cancer cells and contribute to the cell’s behavior.

Proto-oncogenes are the genes that help normal cells grow and divide. These are good because there are controls in place to make sure that the cells function properly. When the cells mutate, they can become oncogenes, which stimulate cancer cell growth and aid in the immortality of these cells.

Tumor suppressor genes are also found within cells. They signal cells to stop growing, repair DNA that has been damaged, or signal cells to die off. Tumor suppressor genes lead to cancer when they are inactive because cells stop going through their usual life cycle.

How Cancer Cells Divide and Grow

If you think about how we started in the womb, it will help explain how cells grow.

We all started as a single cell. This cell essentially cloned itself and became two cells. One becomes two, two becomes four, four becomes eight, and so on. Cells duplicate all the time on a schedule as dictated by the needs of the body, and cancer cells duplicate in the same way.

Normal cells cluster together to form different body parts and different functions throughout the body. They continue to perform their specific job for their entire lifespan and don’t waver from their duties.

As cells become abnormal through a series of mutations, their understanding of the purpose of a normal cell becomes damaged. If only a few abnormal cells are present, they are kept under control by the immune system. However, if cancer cells start replicating, they do not behave like normal cells, and will start invading the healthy cells.

Does the Presence of Cancer Cells Mean You Have Cancer?

When cells start to divide uncontrollably and form tumors, that’s when it can be classified as a cancerous disease.

In many instances, a mass is the result of the over-development of cells. Not all tumors are cancer, as they can be benign, but they should still be looked at by a medical professional.

Doctors can remove and biopsy the tumor to see if it’s cancer, which will enable you to know if it’s a benign or malignant tumor.

Triggers for Cancer Cell Growth

There are a few factors that stimulate the growth of cancer cells. About 40 percent of cancers are thought to be the result of genetic factors, and over half of cancers are attributed to a person’s environment and other factors.

Genetic predisposition to cancer does not guarantee that you will get cancer, but if a few mutations are already encoded in your genetics, it takes less acquired mutations for a cell to become cancerous.

Lifestyle choices and environmental exposures that can also trigger cancer cell growth are obesity, eating red and processed meat, smoking and alcohol consumption, UV exposure, and lack of physical activity.

Cancer Cells and the Immune System

A lot of cancer cells are detected and removed by our immune systems when it is capable of performing properly. Cancer cells can invade the immune system, which protects the body from infections and other conditions, and this invasion may overwhelm the immune system.

There are some cancer cells which stay alive by evading detection from this system that serves to keep our bodies healthy. Other cancer cells can inactivate the immune cells that should remove them from the body. When the immune system is compromised, it makes treatment for cancer a bit more complex.

Types of Cancer Treatments


Common treatments for cancer are surgery, chemotherapy, and radiation. The purpose of surgery is to remove the cancer by cutting it out of the body, but this method cannot be used for all types of cancers.

Chemotherapy uses drugs to kill cancer cells and inhibit their growth, and it’s available through IV or pill form. Chemotherapy is a useful treatment for cancer that has spread because the treatment goes to nearly all parts of the body.

Radiation kills or slows the growth of cancer cells and this method is used alone or in tandem with surgery or chemotherapy. Your doctor will be able to advise which treatment will be the most effective for you.

Cancer is a genetic disease caused by changes to the genes that control how our cells work, grow, divide, and eventually die. When these cells become abnormal, the risk of contracting cancer increases. For many people, cancer can be treated well enough to give them back the quality of life they deserve.