What It Means If You Have Precancerous Cells

The term precancerous cells can be scary, and it's important to note that not all precancerous cells turn into cancer. In fact, most do not. Precancerous cells are abnormal cells that are found on the continuum between normal cells and cancer cells.

Unlike cancer cells, precancerous cells do not invade nearby tissues or spread to distant regions of the body. There are many potential causes of precancerous cells, ranging from infection to chronic inflammation.

Many people have heard of precancerous cells of the uterine cervix that are found during Pap smears, but precancerous cells may occur in nearly any region of the body—the bronchi, the skin, the breasts, the colon, and more.

what are precancerous cells

Verywell / Ellen Lindner


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

The concept of precancerous cells is confusing because it isn’t a black-and-white issue. 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.

It’s important to emphasize again that cells that are precancerous are not cancer cells. This means that left alone, they're not invasive—that is, 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 precancerous cells are removed before they become cancerous, the condition should, theoretically, be 100% curable. That said, not all precancerous cells need to be immediately removed.

Another point of confusion is that cancer cells and precancerous cells can co-exist. As an example, in some people diagnosed with breast cancer, there are other regions in the breasts and even in the tumor itself in which precancerous cells are found as well. In many tumors, both malignant and premalignant cells are found.

Types of Precancerous Conditions

Cancers which begin in epithelial cells (roughly 85% of cancers) may have a precancerous state. This is in contrast to cancers, such as sarcomas, which begin in mesothelial cells. Some precancerous states include:

Again, it's important to note that precancerous cells may or not may not go on to become cancerous cells.

Degrees of Dysplasia Changes

The word "dysplasia" is often used synonymously with precancerous cells, yet there are a few differences. When healthcare providers speak of dysplasia, they are speaking of abnormal cells that could become cancerous.

But in some cases, the term "severe dysplasia" is used to describe cells that are already cancerous but contained within the tissues in which they began—something known as carcinoma in situ.

Precancerous changes are usually described in degrees or levels of abnormalities. There are two primary ways that these are described: severity and grade.


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 clearer is the cervical dysplasia found on some Pap smears. Cells that are mildly dysplastic rarely become cancerous.

There is confusion regarding 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 are cancerous cells that have not yet broken through what is known as the basement membrane.


Another way to describe the severity of precancerous changes in cells is by grades. With cervical cells, these classifications are usually used when a biopsy is done after finding dysplasia on a pap smear.

  • Low-grade dysplasia: Low-grade changes are unlikely to progress to cancer.
  • High-grade dysplasia: Cells with high-grade dysplasia 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.


There are multiple factors that can cause cells to become precancerous, and these vary depending upon the particular type of cells involved. In the past, researchers believed the damage was done when a cell was transformed to a precancerous state by carcinogens in the environment.

We are now learning (in a field called epigenetics) that our cells are more resilient than that and factors in our environment (whether carcinogens, hormones or perhaps even stress) work together to determine what direction abnormal changes in a cell may go.

A simplistic way of understanding causes is to look at influences in the environment that might damage healthy cells, leading to changes in the cell’s DNA, which can subsequently lead to 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).

Infection with the human papillomavirus (HPV) can cause inflammation, leading to precancerous cells in the cervix. HPV is also an important cause of dysplasia that precedes many head and neck cancers, such as tongue cancer and throat cancer.

Most infections with HPV clear before any abnormal cell changes take place. If dysplasia develops, it may resolve on its own or with treatment, or progress to cervical cancer without treatment.

Infection and subsequent inflammation with the bacteria Helicobacter pylori (H. pylori) can result in chronic atrophic gastritis, an inflammatory precancerous change in the lining of the stomach that can lead to stomach cancer.

Chronic Inflammation

Chronic inflammation in tissue can lead to precancerous changes that may in turn progress to cancer. An example is in people who have gastroesophageal reflux disease (GERD) for a prolonged period of time. Chronic inflammation of the esophagus 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. An important area of research is determining whether or not removing areas of high-grade dysplasia will decrease the risk of developing 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.

Chronic Irritation

Chronic irritation of the airways from tobacco smoke, air pollution, and some industrial chemicals can result in bronchial dysplasia (dysplasia of the bronchi). If this is detected early—during a bronchoscopy and a biopsy, for example—the precancerous cells may sometimes be treated with cryosurgery before they have the opportunity to progress to lung cancer.

Latency and Progression

Discussing precancerous changes is a good opportunity to talk about another difficult-to-understand concept in the development of cancer: 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 perplexed when they develop lung cancer even when they quit smoking three decades earlier.

When cells are first exposed to a carcinogen, the damage is done to the DNA in the cell. It's usually an accumulation of this damage (accumulation of mutations) over time that results in a cell becoming precancerous.

Following that period, the cell may progress through stages of mild to moderate—and on to severe—dysplasia before finally becoming a cancer cell. The cell may also be exposed to an environment that inhibits its progression to cancer, or even reverts it to a normal cell. That's why a healthy diet and exercise are important even if you’ve been exposed to a carcinogen.

This is a simplistic way of describing the process, and we are learning that it is much more complex than we once thought. But understanding the precancerous process does help explain the latency period we see with many cancers.

When Do Cells Become Cancerous?

The answer is that most of the time, we don’t know how long it takes for precancerous cells to become cancerous. In addition, the answer certainly varies depending on the type of cell studied.

In one study looking at 101 people with dysplasia of the vocal cords, 15 went on to develop invasive cancer (one had mild dysplasia, one had moderate dysplasia, seven had severe dysplasia and six had carcinoma in situ).

In 73% of these patients, their precancerous lesions became invasive cancer of the vocal cords within one year, with the remainder developing cancer years later.

Precancerous Progression Terms

There are many terms describing cells that make understanding this topic difficult, so an example might help make this understanding a little clearer.

With squamous cell lung cancer, it appears that cells go through a certain progression before cancer develops. It begins with normal lung cells. The first change is hyperplasia, which is defined as cells that grow larger or faster than expected.

The second step is metaplasia, when cells change to a type of cell not usually present. Metaplasia in the esophagus (which can be a precursor to esophageal cancer), for example, is when cells that look like those normally found in the small intestine are found in the esophagus.

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


Precancerous cells are often present without any symptoms. If symptoms are present, they will depend on the location of the precancerous changes.

Precancerous changes in the cervix, for example, may cause the cells to slough more easily, resulting in abnormal uterine bleeding. Precancerous changes in the mouth may be visualized as white spots (leukoplakia).

Precancerous changes in the digestive tract (such as the esophagus, stomach, or colon) may be seen on procedures such as upper GI endoscopy or colonoscopy.

And in regions that are not visible to the naked eye, such as the tissue lining the airways, dysplasia is most often detected 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.


The treatment of precancerous cells will again depend upon the location of the cells. Sometimes close monitoring is all that is recommended to see if the level of dysplasia progresses or resolves without treatment.

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

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 recurrent problems with Pap smears in the future. And if Barrett’s esophagus is treated with cryotherapy, you will still need to have your esophagus monitored at intervals in the future.

For some abnormalities, your healthcare provider may recommend chemoprevention. This is the use of a medication that reduces the risk of cells' becoming abnormal in the future.

An example of this is to treat an infection with the H. pylori bacteria in the stomach. Ridding the body of the bacteria appears to reduce 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.

A last and important point to make is a reminder that, in some cases, the progression of precancerous changes may be altered by our environment: the foods we eat, the 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, avoiding substances that may be responsible for precancerous changes (such as tobacco) may reduce the risk of precancerous cells progressing or the formation of further precancerous cells in the future.

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

Reducing Your Risk

It's never too late to adopt preventive practices—even if you've been diagnosed with cancer.

People who have cancer can also benefit from learning about cancer risk reduction or the reduction of recurrence through diet and exercise.

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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Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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