What It Means If You Have Precancerous Cells

The term precancerous cells can sound scary. The first thing to make clear is that not all precancerous cells turn into cancer. In fact, most do not. But these are abnormal cells, somewhere between normal cells and cancer cells.

Many people have heard of precancerous cells of the uterine cervix that are found during Pap smears. Precancerous cells, however, may occur in nearly any region of the body, such as the skin, the breasts, or the colon. Unlike cancer cells, they do not invade nearby tissues or spread to distant regions of the body.

This article takes a deeper look at what precancerous cells do and how serious they may be when found. It details some possible causes of precancerous cells and how they may be treated.

what are precancerous cells

Verywell / Ellen Lindner


Precancerous cells are also called premalignant cells. They are defined as abnormal cells that could turn into cancerous cells, but which, by themselves, are not invasive or spreading.

The concept of precancerous cells, and whether they progress or not, may sometimes be confusing. That's because the answer isn’t always certain. In general, cells don’t go from normal on day one, to premalignant on day two, and then on to cancer on day three.

Sometimes precancerous cells progress to cancer, but more often they don't. They may stay the same—that is, remain abnormal but not invasive—or they may even become normal again.

Again, it’s important to note that cells that are precancerous are not cancer cells. This means that left alone, they will not spread to other regions of the body. They are simply abnormal cells that could, in time, undergo changes that would transform them into cancer cells.

If the cells are removed before they become cancer cells, then the condition should, in theory, be 100% curable. That said, not all precancerous cells need to be removed right away.

Another point of confusion is that cancer cells and precancerous cells occur together in many tumors. For example, some people with breast cancer have cancer cells in a tumor, but there may be other regions in the breasts and even in the tumor itself in which precancerous cells are found as well.

Types of Precancerous Conditions

Cancers that begin in epithelial cells (roughly 85% of cancers) may have a precancerous state before they turn into cancer. These cells are found in the skin and the lining tissue of many organs.

Some precancerous conditions include:


Precancerous cells are abnormal cells that may arise in the colon, the skin, and many other parts of the body. They are not cancer cells, but neither are they normal cells. Most of these cells will not progress into a cancer. They have changed in ways that suggest it is possible, though, for a cancer to develop.

Dysplasia Meaning

The word "dysplasia" is often used to mean the same thing as "precancerous cells," yet there are a few differences. In many cases, when healthcare providers speak of dysplasia, they are indeed talking about these abnormal cells that could turn into cancer cells.

But in some cases, the term "severe dysplasia" is used to describe cells that are already cancerous. They are still contained within the tissues in which they began and have not spread. This is known as carcinoma in situ.

Precancerous changes are usually described in degrees or levels of abnormality. Severity and grade are the two main ways that are used to describe them.


Dysplasia can range from mild to severe:

  • Mild dysplasia: Mild dysplasia refers to cells that are just slightly abnormal. These cells do not usually progress to cancer.
  • Moderate dysplasia: These cells are moderately abnormal and have a higher risk of developing into cancer.
  • Severe dysplasia: This is the most extreme abnormality seen before a cell would be described as cancerous. Severe dysplasia is much more likely to progress to cancer.

An example that might make this more clear is the cervical dysplasia found on some Pap smears. Cells that show a mild dysplasia rarely become cancer cells.

There is a bit of confusion on where exactly to draw the line between severe dysplasia and carcinoma in situ. Carcinoma in situ is a term literally translated as “cancer in place.” These cancer cells have not yet broken through what is known as the basement membrane. They have not spread.


Another way to describe how severe any precancerous changes in cells have become is by using a grading system. With cervical cells, these grades are usually used when a biopsy is done after finding dysplasia on a Pap smear.

  • Low-grade dysplasia: Low-grade cell changes are unlikely to progress to cancer.
  • High-grade dysplasia: High-grade cell changes are much more likely to progress to cancer.

An example of this would be low-grade dysplasia seen on a biopsy of the cervix. The likelihood of these changes progressing to cancer is fairly low. In contrast, high-grade colon dysplasia associated with colon polyps has a high risk of continuing on to become colon cancer.


Dysplasia describes physical changes in cells that are identified when they're seen under a microscope. These changes may be mild, moderate or severe. The changes also may be called low- or high-grade. The risk that these cells may become cancer cells is greater when they are found to be severe or show high-grade dysplasia.


There are quite a few factors that can cause cells to become precancerous. They vary depending upon the particular type of cells involved. In the past, researchers believed that the damage was done by carcinogens, or cancer-causing agents in the environment, that transform healthy cells into abnormal ones.

Scientists who work in a field called epigenetics are now learning that the cells in our body are more resilient than that. A host of factors, such as carcinogens, hormones, or perhaps even stress, work together. The combination is what determines how abnormal changes in a cell may progress.

One way of understanding causes is to look at the possible reasons for why damage may happen to healthy cells, leading to the genetic changes that in turn drive abnormal growth and development.


Infections with viruses, bacteria, and parasites are responsible for 15% to 20% of cancers worldwide. This figure is lower in the U.S. and other developed countries.

For example, a human papillomavirus (HPV) infection can cause inflammation leading to precancerous cells in the cervix. Most HPV infections clear before any abnormal cell changes take place. If dysplasia does begin, it may go away on its own or with treatment.

On the other hand, it also may progress to cervical cancer if it is not treated. HPV is also an important cause of dysplasia that may progress into head and neck cancers, such as tongue cancer and throat cancer.

Another example is Helicobacter pylori (H. pylori) infection. These bacteria cause inflammation and can result in a condition called chronic atrophic gastritis. This may lead to precancerous changes in the lining of the stomach, which in turn may progress into stomach cancer.

Chronic Inflammation

Chronic (persistent) inflammation in tissue can lead to precancerous changes. An example is in people who have gastroesophageal reflux disease (GERD) for a prolonged period of time. The inflammation of the esophagus caused by stomach acids can result in a condition known as Barrett’s esophagus.

Among people with Barrett’s esophagus, approximately 0.5% per year will develop esophageal cancer. One important area of research is to learn whether or not removing areas of high-grade dysplasia caused by the condition will lower the risk of it turning into esophageal cancer.

Another example is inflammation of the colon in people with inflammatory bowel disease (IBD). IBD can lead to polyps with colon dysplasia, which in turn can eventually lead to colon cancer.

Chemical Exposure

Chronic exposure to tobacco smoke, air pollution, and some industrial chemicals can result in dysplasia of the bronchi, the main airways into the lungs. If this is found early, the precancerous cells may sometimes be treated with cryosurgery. This is a procedure for freezing the cells to halt their growth before they have a chance to become lung cancer.

Latency and Progression

A discussion of precancerous cell changes offers a good opportunity to talk about another concept that can be hard to grasp. This is called latency.

The latency period is defined as the period of time between exposure to a cancer-causing substance (a carcinogen) and the later development of cancer.

People are often surprised when they develop cancer many years after exposure to a carcinogen. For example, some people are diagnosed with lung cancer even when they quit smoking three decades earlier.

Genetic damage is done when cells are first exposed to a cancer-causing agent. But it's usually an accumulation of this damage, and the genetic mutations involved over time, that causes a cell to become precancerous.

The cell may then progress through stages of mild to moderate—and on to severe—dysplasia before finally becoming a cancer cell. This progress toward cancer also may be limited by other factors in its environment, or it may even revert back into a normal cell. That's why a healthy diet and exercise are important even if you’ve been exposed to a carcinogen.

The process is much more complex than once thought, but understanding the basics does help to explain the latency period seen with many cancers.

When Do Cells Become Cancerous?

Most of the time, the answer to how long it may take for a precancerous cell to become cancerous will vary. The answer also depends on the type of cell that's involved.

In one study that looked at 101 people with abnormal cell changes of the vocal cords, 15 of them went on to develop invasive cancer.

One of those had mild dysplasia, one had moderate dysplasia, seven had severe dysplasia, and six had carcinoma in situ. In 73% of these people, their precancerous lesions became invasive cancer of the vocal cords within one year. The rest of them developed cancer years later.

Terms Describing Progression

There are many terms describing cells that may seem difficult. Another example may help to make these concepts more clear.

With squamous cell lung cancer, it appears that cells progress in a certain way before cancer develops. It begins with normal lung cells. The first change is hyperplasia, which means that the cells grow larger or faster than expected.

The second step is metaplasia. Here, the cells change to a type of abnormal cell not usually present. Metaplasia in the esophagus, for example, is when cells are present that look like those normally found in the small intestine. This may lead to esophageal cancer.

The third step is dysplasia, followed by carcinoma in situ and, finally, invasive squamous cell carcinoma.


People who have precancerous cells often have no symptoms. If symptoms are present, they will depend on the location of these cell changes.

In the cervix, for example, the cell changes may cause abnormal uterine bleeding. Or, precancerous changes in the mouth may appear as white spots.

In the stomach, colon, and other parts of the digestive tract, the precancerous changes may be seen during colonoscopy, upper GI endoscopy, and other procedures.

And in regions that are not visible to the naked eye, such as the tissue lining the airways, dysplasia is most often found when a screening biopsy is done for another reason.


A physical exam or imaging studies may suggest that abnormal cells could be present, but a biopsy is necessary to make the diagnosis. After a section of tissue is removed, pathologists look at the cells under the microscope for signs that cells are precancerous or cancerous. They can determine the stage and grade of the cells.


The treatment of precancerous cells also depends on where in the body they are located. In some cases, close monitoring is all that is recommended to see if the level of dysplasia progresses or if it goes away without any treatment.

Often, the precancerous cells will be removed by a procedure such as cryotherapy (freezing the cells) or surgery to remove the region where the abnormal cells are found.

Even if the abnormal cells are removed, it’s important to keep in mind that whatever caused the cells to become abnormal in the first place may affect other cells in the future, and careful monitoring over the long term is important.

If abnormal cervical cells are treated with cryotherapy, it will still be important to monitor for future problems with Pap smears. And if Barrett’s esophagus is treated with cryotherapy, you will still need to have the health of your esophagus tissue monitored in the future.

For some abnormalities, your healthcare provider may recommend chemoprevention. This is the use of a drug that reduces the risk of cells becoming abnormal again later.

Treating an H. pylori infection, for example, will remove the bacteria from the stomach. It appears to reduce the precancerous cells and the development of stomach cancer.

Researchers are looking at the use of several medications and vitamins to see if their use in former and current smokers will lower their risk of developing lung cancer in the future.

Remember too that, in some cases, the progression of precancerous changes may be affected by environmental factors. They include the foods we eat, how much exercise we get, and the lifestyle choices we make. A diet rich in foods containing certain vitamins, for example, may help the body clear the HPV virus more rapidly.

Similarly, it's important to consider tobacco and other substances that may be responsible for precancerous changes. Avoiding them may reduce the risk that abnormal cells will progress or that other precancerous cells will develop in the future.

An example is the situation with smoking and cervical cancer. While smoking does not appear to cause cervical cancer on its own, smoking combined with an HPV infection increases the chance that a cancer will develop.


Precancerous cells are cells that show abnormal changes but have not yet developed into cancer cells. In many cases, they won't. But cancers can develop from these changes, so it's important to find them through routine screenings and other measures.

The abnormal changes seen in these cells arise from a number of causes, which may include infection, inflammation, or environmental exposure. Some precancerous cells will require only monitoring. Treatment for others will depend on where they are and what may have caused them.

Be sure to discuss any precancerous cells and the appropriate next steps with your healthcare provider.

A Word From Verywell

It's never too late to adopt preventive practices—even if you've been diagnosed with cancer. People who have cancer also may benefit from learning about how to reduce cancer risk or prevent its recurrence. Diet, exercise, and other healthy lifestyle choices can help.

Take a moment to check out tips on reducing your risk of cancer, which can be helpful in reducing lung cancer and other cancers, as well as dietary superfoods which may help to lower your risk of either cancer or cancer recurrence.

Frequently Asked Questions

  • How serious are precancerous cells?

    Precancerous cells may or may not turn into cancer over time. Because those cells are abnormal, it's important to have them monitored or sometimes removed to help reduce your risk of cancer down the road.

  • How are precancerous cervical cells treated?

    Treatments for precancerous cervical cells may include:

  • What do precancerous skin cells look like?

    A precancerous skin growth, called actinic keratosis, may not be visible at first. Sometimes you may feel it on your skin as a rough spot that's like sandpaper. It may also appear as a reddish spot on your skin. Your dermatologist can help you to identify these precancerous spots and remove them to make sure they don't turn into squamous cell carcinoma.

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By Lynne Eldridge, MD
 Lynne Eldrige, MD, is a lung cancer physician, patient advocate, and award-winning author of "Avoiding Cancer One Day at a Time."