Carcinoma in situ is when cell changes show up as cancerous under a microscope, but they have not spread beyond where they first formed. The words “in situ” mean “in its original place.”

These in situ cells are not malignant, or cancerous. However, they can sometime become cancerous and spread to other nearby locations. Doctors may also talk about precancerous cells.

Other names for carcinoma in situ are:

  • stage 0 cancer
  • noninvasive cancer
  • preinvasive cancer

This article will look at some common areas where carcinoma in situ occurs, and the treatment options.

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If a person has carcinoma in situ, they may not notice any symptoms, unless the changes affect the skin, the mouth, or other visible parts of the body.

Symptoms to look out for in these areas include:

Skin: There may be changes in the color or texture of the skin and possibly the nails.

Mouth: White patches may appear in the mouth.

Eyes: If changes occur in the cornea, the person may have a feeling of irritation or burning that does not go away.

Sometimes, a lump will appear, for example, in the breast. Not all lumps or tumors are cancerous. A biopsy will show whether it is cancer (malignant) or not.

For other types of carcinoma in situ, routine screening and laboratory tests can detect precancer at an early stage. These tests can help to avoid the development of cancer later.

When other symptoms of cancer appear, such as fatigue or loss of appetite, this usually means the carcinoma is no longer in situ. Instead, it may be starting to grow and spread and may have become cancerous. However, as long as the cells are in situ, and within a limited area, effective treatment is possible.

Carcinoma in situ can appear anywhere in the body because cancer always begins with changes in a few cells. Here are just a few of the types.

The bladder

Papillary urothelial carcinoma is a type of bladder cancer that involves small, finger shaped growths. These often remain in situ, which means they do not spread to other areas.

However, around 10–15% become invasive, or cancerous.

Learn more about papillary urothelial carcinoma here.

The cervix

Many women have a routine Pap smear test to check for cervical cancer. A possible result of this test is cervical carcinoma in situ. This finding means that there are precancerous cells on the surface layer of the cervix.

These in situ cells are not cancer, but they could become malignant. If they do this, they can start to invade other tissues.

For this reason, a doctor will recommend treatment to remove the cells. This will reduce the risk of cancer developing later.

Learn more here about the Pap smear.

Breast cancer

Ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS) happen when changes occur in breast cells.

These conditions are not cancer. The cells are noninvasive, and they may not spread. However, precancerous cells may become invasive at a later date, so it is best to remove them.

Ductal means that cells are growing in the milk ducts of the breasts. Lobular means they are growing in the lobules of the milk producing glands.

Around 60,000 people have a diagnosis of DCIS in the United States every year. This figure is approximately 20% of all new breast cancer diagnoses. People can have surgery or surgery and radiation therapy to remove DCIS.

If a person has surgery, they have a 25–30% chance of DCIS coming back at some time. With surgery and radiation therapy, there is a 15% chance that DCIS will recur.

If the condition recurs, it will still not be invasive, although it may become so in the future.

Find out more about breast cancer, how to recognize the changes, and what to expect.

The skin

Squamous cell carcinoma in situ refers to changes in skin cells that could become cancerous. The changes are on the surface layer of the skin only.

The cells most commonly appear where the skin has exposure to the sun, such as the face, ears, and neck.

If a person notices the following skin changes, they should see a doctor:

  • areas of raised, smooth, shiny, pearly looking skin
  • patches that look like a scar and are firm, yellow, white, or waxy
  • raised and red or red-brown patches
  • scaling, peeling, or crusting

As with other types of carcinoma in situ, this does not mean the person has cancer. However, they have precancerous cells that could become cancerous and invasive without treatment.

For this reason, a doctor will often remove areas of skin where this type of cell has formed.

Learn more here about how to recognize the signs of skin cancer.

The mouth

The mouth is another area where a person might ask a doctor about changes they have noticed.

A person who notices white patches in their mouth with a flat, thin appearance should see their doctor for an assessment.

This is particularly so if the patch or patches do not disappear when the person rubs or the individual is a smoker.

Sometimes a patch may have a white color with some red in it, or an irregular surface, which may be flat, nodular, or warty.

The changes may affect the gums, tongue, lips, inside the cheeks, or the roof of the mouth.

As with other in situ carcinomas, this development is not cancer. However, a person with these patches should seek treatment, as they have a higher chance of developing cancer in future.

If people are smokers, they will have to consider quitting.

Find out more here about mouth cancer.


Carcinoma in situ can affect the eyes, including the conjunctiva, which is the mucous membrane that covers the front of the eye.

Symptoms include:

  • feeling as if something is in the eye
  • a burning sensation
  • a visible tumor
  • red eye

Without treatment, this type of carcinoma in situ can eventually invade other nearby tissues. However, it rarely spreads to more distant parts of the body. One possible treatment is surgical removal of the cells with cryotherapy.

What are the signs of eye cancer, and what is the treatment? Learn more here.

Treatments for carcinoma in situ will depend on factors, such as:

  • the location of the precancerous cells
  • the size and location of any benign tumor
  • individual risk factors, for example, a personal or family history of cancer
  • the age of the person
  • other health conditions
  • personal preferences

Treatment options

A doctor may recommend different types of surgery, such as:- open surgery, such as a mastectomy for breast cancer or a preventive hysterectomy for cervical cancer

  • laser surgery
  • loop electrosurgical excision procedure (LEEP/LEETZ)
  • cold knife conization
  • cryotherapy, using a freezing technique to remove cells
  • excision of a skin patch

Sometimes, the doctor will recommend radiation therapy to ensure that treatment removes all the cells.

A doctor will help the individual choose the right treatment, depending on the type of carcinoma in situ and individual factors.

A diagnosis of carcinoma in situ does not mean a person has cancer, nor does it mean they will have cancer in the future. However, it increases the risk of cancer developing, so doctors usually recommend treatment.

A person can lower their risk of many types of carcinoma in situ by living a healthful lifestyle, including avoiding smoking and using sun protection when outdoors.

Knowing how to recognize changes in the skin, mouth, and other parts of the body can help a person look for signs that they may need medical attention.

Screening programs for breast cancer, skin cancer, prostate cancer, and other types of cancer can help a doctor detect carcinoma in situ in the early stages. This means they can treat it before it has a chance to become cancerous.


I have had various patches of skin cancer removed, but new ones keep appearing in different places. Is this carcinoma in situ?


Developing awareness of your skin changes is a great first step.

The fact that you noticed new patches in different places allows you to alert your doctor as soon as possible for further testing and treatment. Though it seems logical that, after having had various patches of skin cancer removed, these new patches can be carcinoma in situ, it’s not readily identifiable by just looking at your skin.

You definitely need a specialist, such as an oncology and melanoma specialist, to do an evaluation. A carcinoma in situ diagnosis must come from a doctor’s office after careful testing and evaluation.

Christina Chun, MPH Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

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