Carcinoma in situ is when cell changes appear cancerous under a microscope but 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 sometimes become cancerous and spread to nearby locations beyond the layer of the organ where they originated. Doctors may also use the term precancerous cells.

Other names for carcinoma in situ are:

  • stage 0 cancer
  • noninvasive cancer
  • preinvasive cancer

This article will outline 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 body parts.

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 feel irritation or burning that does not go away.

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

For other types of carcinoma in situ, routine screening and laboratory tests can detect precancer at an early stage. These tests can help prevent cancer from developing 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, effective treatment is possible as long as the cells are in situ and remain within a limited area.

Learn all there is to know about carcinomas.

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 bladder cancer.

The cervix

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

These in situ cells are not cancer, but they could become malignant. If this happens, 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 about the Pap smear.

Breast cancer

Ductal carcinoma in situ (DCIS) and lobular carcinoma in situ (LCIS) occur due to changes in breast cells.

These conditions are not cancer. The cells are noninvasive and 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.

According to the Breast Cancer Research Foundation, around 56,000 people receive a diagnosis of DCIS in the United States every year. This figure represents approximately 20–25% of all new breast cancer diagnoses. People can have surgery or surgery and radiation therapy to remove DCIS.

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

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 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 important if the patch or patches do not disappear when the person rubs them,

Sometimes, a patch may have a white color with some red 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 the future.

Anyone who smokes will have to consider quitting.

Find out more 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 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.

Learn more about the signs and treatment of eye cancer.

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, including open surgery, such as a mastectomy or lumpectomy for breast cancer or a preventive hysterectomy for cervical cancer.

Other treatments include:

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.

Learn the differences between a mastectomy and a lumpectomy.

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 adopting certain lifestyle habits, such as using sun protection when outdoors and avoiding smoking if they smoke.

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 becomes 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.

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