Squamous Cell Carcinoma In Situ of the Larynx: Understanding Your Pathology Report

Section Editor: Jason Wasserman MD PhD FRCPC
July 26, 2026

Squamous cell carcinoma in situ of the larynx is a very early, non-invasive form of cancer in the lining of the voice box. The lining is made of squamous cells, flat cells that sit in a thin surface layer called the epithelium. In carcinoma in situ, these cells look severely abnormal throughout the full thickness of that layer but remain confined to it and have not grown into the tissue underneath. The term “in situ” means “in its original place.”

The key point is what separates this from an invasive cancer. As long as the abnormal cells stay within the surface layer, they cannot reach blood vessels or lymph nodes, so they cannot spread to other parts of the body. Because of this, carcinoma in situ is highly treatable and is usually cured by removing the abnormal area. Left untreated, however, it carries a high risk of developing into an invasive squamous cell carcinoma, which can spread. That risk is why the diagnosis is treated rather than watched.

You may also see this same finding described on your report as severe dysplasia or high-grade dysplasia. In the larynx, these terms describe the same degree of change and are often used interchangeably, with carcinoma in situ sometimes reported as a separate highest category. If your report uses one of these other terms, it is describing the same thing, and this article applies.

Carcinoma in situ develops most often on the vocal cords, in the part of the larynx called the glottis, and it usually affects adults over the age of 40.

This article explains the findings you are likely to see on a pathology report for squamous cell carcinoma in situ of the larynx, what each one means, and why it matters for your care.

Is squamous cell carcinoma in situ cancer?

Squamous cell carcinoma in situ is considered the earliest form of cancer because the cells show the same severe abnormalities seen in invasive cancer. The important difference is that it is non-invasive. The abnormal cells sit entirely within the epithelium and are separated from the deeper tissue by a thin barrier called the basement membrane, which they have not broken through.

This distinction is what makes the diagnosis far less dangerous than invasive cancer. In an invasive squamous cell carcinoma, the tumor cells have broken through that barrier into the deeper tissue, called the stroma, where they can reach blood vessels and lymphatic channels and travel elsewhere. Because the cells in carcinoma in situ have not done this, they cannot spread to lymph nodes or to distant parts of the body while the condition remains in situ. For the same reason, this diagnosis is not given a tumor stage in the way an invasive cancer is, since staging measures how far a cancer has spread and an in situ cancer has not spread at all.

What causes squamous cell carcinoma in situ of the larynx?

Squamous cell carcinoma in situ of the larynx develops when the squamous cells lining the voice box are damaged repeatedly over many years, until enough errors build up in their genetic material that the cells grow abnormally. The main causes are:

Tobacco. By far the most important cause.
Alcohol. Heavy use raises risk on its own, and combining it with smoking raises risk considerably more than either alone.
Previous radiation to the neck. Radiation given years earlier for another condition can lead to changes in the treated area.
A weakened immune system. This includes long-term immune suppression after an organ transplant.

Because the whole lining of the larynx has usually been exposed to the same irritants, a new abnormal area can develop elsewhere in the voice box even after the first has been successfully treated. This is one of the main reasons follow-up continues over the long term.

What are the symptoms of squamous cell carcinoma in situ of the larynx?

Because carcinoma in situ usually develops on the vocal cords, the most common symptom is a change in the voice, since even a small abnormal area interferes with the way a vocal cord vibrates. Symptoms include:

Hoarseness or a change in the voice, often the first and only symptom
A rough, strained, or breathy voice quality
Throat discomfort or a feeling of something in the throat
Difficulty swallowing, which is less common
Noisy breathing or shortness of breath, only when a larger area is involved

Any change in the voice lasting more than two to three weeks should be assessed by an ear, nose, and throat specialist. Hoarseness appearing early is genuinely useful here, because it often brings the change to attention while it is still confined to the surface.

How is the diagnosis made?

The diagnosis is made when a pathologist examines tissue from the abnormal area under the microscope. A specialist may see a white or thickened patch on the vocal cord when examining the larynx, but the appearance alone cannot establish the diagnosis or determine whether an invasive cancer is present.

The tissue is obtained by biopsy during a procedure called microlaryngoscopy, in which a thin scope is passed through the mouth under general anesthetic so the surgeon can see the vocal cords directly and remove the abnormal area or take a sample.

Under the microscope, the pathologist looks for severely abnormal squamous cells affecting the full thickness of the epithelium, with the normal orderly maturation from the base to the surface lost. Your report may also note keratinization, meaning the cells are producing keratin, a tough protein that is normal in skin but not in the lining of the larynx. The single most important thing the pathologist checks is whether the abnormal cells have broken through the basement membrane into the deeper tissue. In carcinoma in situ, they have not. If they had, the diagnosis would instead be invasive squamous cell carcinoma.

Because a small biopsy sample only part of the abnormal area, and the region sampled is not always the most abnormal one, the whole area is often removed rather than just sampled. This allows it to be examined completely so that an invasive cancer is not missed.

Surgical margins

When the abnormal area is removed, the report may describe the margins, the cut edges of the tissue removed. Margin status shows whether the whole abnormal area was taken out.

Negative (clear) margin. No abnormal cells at the cut edge. The area appears to have been completely removed, which is associated with a lower chance of the condition returning.
Positive (involved) margin. Abnormal cells reach the cut edge, meaning some may remain. Your doctor may discuss removing more tissue or monitoring the area closely.
Cannot be assessed. The tissue was fragmented, or the edges were cauterized during removal, which is common with laser procedures. This does not mean the procedure was inadequate, but it makes careful follow-up more important.

Two points are specific to the larynx. First, the surgeon works to remove the abnormal area while preserving as much normal vocal cord as possible, because taking too much tissue affects the voice, so margins here are often narrower than they would be elsewhere in the body. Second, a clear margin means the abnormal-looking tissue was removed, not that the risk has been eliminated, because the surrounding lining may already carry damage while appearing normal. This is why follow-up continues regardless of what the margins show.

What is the risk that carcinoma in situ will turn into invasive cancer?

Squamous cell carcinoma in situ of the larynx is non-invasive, but left untreated it carries a high risk of developing into invasive squamous cell carcinoma. Among the precancerous and non-invasive changes of the larynx, it carries the highest risk, which is why removal is almost always recommended rather than watchful waiting.

Once the area has been completely removed, the outlook is very good, and most people are cured. Two things influence what happens next. The first is whether the area was completely removed, which is what the margin result describes. The second is the fact that the whole lining of the larynx has usually been exposed to the same tobacco and alcohol, so a new abnormal area can develop elsewhere even after successful treatment. Stopping smoking and reducing alcohol are the most effective steps available to lower that ongoing risk.

What happens after the diagnosis?

Treatment is usually complete removal of the abnormal area, most often using a laser through a scope passed into the throat, performed by an ear, nose, and throat surgeon. Removal serves two purposes: it takes out the abnormal tissue, and it allows the whole area to be examined so an unsuspected early invasive cancer is not missed. Radiation is an alternative that may be discussed in some situations, such as when the abnormal area is extensive, when it keeps returning, or when surgery would substantially affect the voice.

Because the condition is non-invasive, removal of lymph nodes is not needed, and chemotherapy has no role.

Regular follow-up examination of the larynx is important even when the margins are clear, since the condition can return at the same site or a new area can appear elsewhere in the voice box. Follow-up generally continues for years rather than a fixed period. Support for stopping smoking and reducing alcohol is a standard part of care and worth asking for. Voice therapy with a speech-language pathologist may also be offered if your voice has changed after a procedure on the vocal cords.

Questions to ask your doctor

Does my report describe this as carcinoma in situ, or as severe or high-grade dysplasia?
Was there any sign of invasion, or were the abnormal cells limited to the surface?
Where in my larynx is the abnormal area, and how much is involved?
Was the whole area removed, or was only a sample taken?
Were the surgical margins clear?
Do I need further treatment, and is radiation an option in my case?
What is my risk of developing invasive cancer?
How often will my larynx be examined, and for how long?
Will my voice be affected, and would voice therapy help?
What help is available to me for stopping smoking and reducing alcohol?
What changes should prompt me to call before my next visit?