What It Means If You Have Precancerous Cells

The term “precancerous cells” can be scary, and it's important to begin talking about these cells by saying 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, but unlike cancer 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. Let’s begin by describing the characteristics of these cells are and how they differ from “normal” cells in our bodies.


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.

This last comment is something relatively new to cancer researchers. In the past, it was 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.

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 percent 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.

Degrees of Dysplasia Changes

The word dysplasia is often used synonymously with precancerous cells, yet there are a few differences.

When doctors speak of dysplasia, they are speaking of abnormal cells that could become cancerous.

But in some cases, the words severe dysplasia are 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.


  • 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. On the other hand, if left untreated, severe dysplasia found on a Pap smear will progress to cancer 30 percent to 50 percent of the time.

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.


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 to look for signs that cells are precancerous or cancerous.


There are multiple factors that can cause cells to become precancerous, and these vary depending upon the particular type of cells involved.

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. A few underlying processes that may cause abnormalities in cells (with a few examples to illustrate) include:

  • Infection: While only 4 to 10 percent of cancers in the U.S. are related to infections, infections with viruses, bacteria, and parasites are responsible for roughly a fourth of cancers worldwide.

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 suffer from 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 one percent 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.

Types of Precancerous Conditions

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

  • Cervical intraepithelial neoplasia (CIN) - A precancerous state of cervical cancer
  • Barrett's esophagus (abnormal esophageal cells which may go on to become esophageal cancer)
  • Atypical lobular hyperplasia (which may develop into breast cancer)
  • Adenomatous polyps in the colon (which may develop into colon cancer)
  • Actinic keratoses (abnormal changes in the skin which may develop into squamous cell skin cancer)
  • Dysplastic moles (which may develop into melanoma)
  • Bronchial epithelial dysplasia (which may develop into lung cancer)
  • Atrophic gastritis (precancerous changes in the stomach which may develop into gastric (stomach) cancer
  • Bowen's disease (precancerous changes that may occur on the vulva or penis)

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

What Is a Latency Period?

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'd 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 (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.

As noted above, cervical cells with severe dysplasia progressed to cancer 30 to 50 percent of the time, but the time frame that this took to happen was variable. In one study looking at 115 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 6 had carcinoma in situ). In 73 percent of these patients, their precancerous lesions became invasive cancer of the vocal cords within one year, with the remainder developing cancer years later.

Are There Symptoms?

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.


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.

For example, 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 doctor 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.

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. For example, hyperplasia of the heart would be the term used to describe an enlarged heart.

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.

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.

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