Keratinizing Squamous Dysplasia of the Oral Cavity: Understanding Your Pathology Report

Section Editor: Jason Wasserman MD PhD FRCPC
July 24, 2026

Keratinizing squamous dysplasia is a precancerous change in the lining of the oral cavity, the medical name for the mouth. It develops in squamous cells, the flat cells that form the surface layer of the mouth’s lining, when they begin to grow and mature abnormally. What distinguishes this form of dysplasia from other types is the excess production of keratin, a tough protective protein normally found in skin, hair, and nails. The inside of the mouth produces relatively little keratin under normal circumstances. When the abnormal cells start producing it in quantity, the lining thickens and the area typically becomes visible as a white patch, sometimes with red areas mixed in.

Keratinizing squamous dysplasia is not cancer. The abnormal cells remain confined to the surface layer and have not grown into the tissue beneath, which is what defines an invasive cancer. What the diagnosis does indicate is an increased risk that squamous cell carcinoma, the most common cancer of the mouth, could develop in that area over time. Most people with this diagnosis never go on to develop cancer, but the risk is high enough that the finding is followed carefully.

Keratinizing squamous dysplasia can develop anywhere in the mouth lined by squamous epithelium. It is found most often on the side and undersurface of the tongue and on the floor of the mouth, which are the highest-risk sites, and also on the inner cheeks, gums, hard palate, and inner surface of the lips.

This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes keratinizing squamous dysplasia?

Keratinizing squamous dysplasia, a precancerous change in the lining of the mouth marked by excess keratin production, develops when the cells of that lining are damaged repeatedly over a long period. Each round of injury and repair leaves behind a small number of errors in the cells’ genetic material. Once enough errors accumulate in the genes controlling growth and maturation, the cells stop behaving normally, and the excess keratin production is part of that disordered behavior.

The main causes and risk factors are:

Tobacco — The strongest and most important modifiable risk factor, in every form: cigarettes, cigars, pipes, and smokeless products such as chewing tobacco and snuff.
Alcohol — An independent risk factor. Alcohol also makes the lining of the mouth more permeable to the chemicals in tobacco, so the two together raise risk more than either alone.
Betel quid and areca nut — A major cause of oral dysplasia in parts of South and Southeast Asia and the Pacific. These substances damage the lining of the mouth directly.
Chronic irritation and inflammation — Long-standing friction from sharp teeth or poorly fitting dental appliances, and inflammatory conditions such as oral lichen planus, are associated with increased risk.
A weakened immune system — People taking immune-suppressing medication, including after an organ transplant, are at higher risk because the immune system is less able to clear abnormal cells.
A previous lesion elsewhere in the mouth — Having had dysplasia or an oral cancer before increases the chance of another area developing.

Keratinizing squamous dysplasia is a separate condition from HPV-associated dysplasia of the oral cavity. The two look different under the microscope and have different causes. If your report describes keratinizing dysplasia, human papillomavirus (HPV) is not the cause, and you should not expect HPV testing on your report.

Dysplasia sometimes develops in people with none of these risk factors, particularly on the tongue, and this does not mean anything was missed. It is also worth understanding that when the whole lining of the mouth has been exposed to tobacco, alcohol, or betel quid over years, the entire surface carries damage, not just the visible patch. Pathologists call this field change. It explains why a new lesion can appear elsewhere in the mouth after the first has been removed, and it is a central reason follow-up continues long term.

What are the symptoms of keratinizing squamous dysplasia?

Most people with keratinizing squamous dysplasia, a precancerous change in the lining of the mouth, have no symptoms, and the condition is frequently found by a dentist or hygienist during a routine examination. Because the defining change is excess keratin production, the most common finding is a visible white patch. When symptoms are noticed they usually include:

A persistent white patch that will not rub off, known clinically as leukoplakia. This is the most common presentation.
A red patch, known clinically as erythroplakia, or a mixed red and white patch. These carry a higher risk of underlying dysplasia than a uniform white patch.
An area of lining that feels thicker, rougher, or firmer than the surrounding tissue.
Soreness, tenderness, or a burning sensation, particularly with spicy, acidic, or hot foods.
In more extensive cases, difficulty chewing, swallowing, or speaking.
Rarely, an ulcer or bleeding.

Because pain is usually absent and the appearance overlaps with many harmless conditions, this diagnosis cannot be made by looking at the mouth. A biopsy is required. Any patch or sore in the mouth lasting more than two to three weeks, and particularly any red patch, should be evaluated.

How is the diagnosis made?

Keratinizing squamous dysplasia is diagnosed only when tissue from the abnormal area is examined under the microscope by a pathologist. The tissue is obtained by biopsy, usually a small piece taken from the most abnormal-looking part of the patch. Neither the appearance of the patch in the mouth nor any imaging test can establish this diagnosis or determine its grade.

Under the microscope, the pathologist assesses three things together: how much keratin the surface is producing and whether the type of keratin is abnormal for that part of the mouth, how abnormal the individual cells look, and how disorganized the lining is as a whole. The pathologist then judges how far up through the thickness of the lining these changes extend and combines this into a grade. Just as importantly, the pathologist confirms that the abnormal cells have not broken through the base of the lining into the tissue below. That downward growth is called invasion, and its absence is what separates dysplasia from invasive squamous cell carcinoma.

Your report may include a few descriptive terms alongside the diagnosis. Hyperkeratosis means a thickened layer of keratin on the surface, and it is what makes the area look white in the mouth. Parakeratosis describes keratin that still contains the remains of cell nuclei. Acanthosis means the lining itself is thickened, and atypia means the cells look abnormal. These terms describe what the pathologist saw. They accompany the diagnosis rather than adding to it, and the grade remains the finding that matters most.

A particular challenge with keratinizing dysplasia is that several harmless conditions produce excess keratin and can look similar. Friction from a sharp tooth or a cheek-biting habit causes a thickened white area that is purely reactive. Candida, a common yeast, causes hypertrophic candidiasis, which thickens the lining and can produce cell changes that mimic dysplasia. Inflammatory conditions such as oral lichen planus produce reactive changes in the cells that can be mistaken for true dysplasia. These can be difficult to tell apart from true dysplasia. That is why your report may mention candida or inflammation alongside the diagnosis, and why a repeat biopsy is sometimes requested after treating an infection or removing a source of friction.

One limitation of the initial biopsy deserves emphasis. A biopsy samples only a small part of the abnormal area, and the region sampled is not always the most abnormal one. In published series of patients whose biopsy showed high-grade dysplasia and who then had the whole area removed, invasive cancer was already present in the removed tissue in roughly 18% of cases. A biopsy result therefore establishes a minimum rather than a maximum, and this is a major reason complete removal is often recommended even when the biopsy shows no cancer.

How is keratinizing squamous dysplasia graded?

The grade is the part of the report on keratinizing squamous dysplasia that carries the most weight, because it is the strongest single predictor of whether the area will progress to cancer. Two grading systems are in use, and different laboratories use different ones, so your report may show either.

The three-tier system. This is the system recommended by the World Health Organization and used by most laboratories. It is based on how far up through the thickness of the lining the abnormal changes extend, judged alongside how severe the cell changes are.

Mild dysplasia — The abnormal changes are limited to the lower third of the lining, at and just above the base.
Moderate dysplasia — The changes extend into the middle third.
Severe dysplasia — The changes extend into the upper third, involving most or all of the thickness of the lining.

The two-tier (binary) system. Some laboratories report dysplasia simply as low-grade or high-grade. Rather than relying on thirds, this system counts features: a lesion is classified high-grade when at least four architectural features and five cytological features are present, regardless of how high in the lining they reach. Mild dysplasia generally corresponds to low-grade and severe dysplasia to high-grade. Moderate dysplasia may be assigned to either, and it is the category where the two systems disagree most.

Carcinoma in situ. Some reports use squamous cell carcinoma in situ as a highest category. In the mouth this term is generally treated as equivalent to severe dysplasia rather than as a separate, more dangerous diagnosis. The word “carcinoma” in that phrase understandably causes alarm, but carcinoma in situ means the abnormal cells still sit entirely within the surface layer and have not invaded. It is not an invasive cancer.

One point is worth knowing, because patients sometimes obtain second opinions and find the grade has changed. Grading dysplasia is a judgment, not a measurement, and agreement between pathologists is only moderate. Published studies find pathologists agree on the exact grade roughly half to two-thirds of the time, although agreement on whether dysplasia is present at all is considerably better. A change in grade on review is common and does not mean an error was made. It is one reason your treatment team weighs the grade together with the size, location, and appearance of the lesion and your risk factors, rather than treating the grade as the only consideration.

Surgical margins

When an area of keratinizing squamous dysplasia is removed completely rather than only sampled, the pathology report describes the margins, the cut edges of the tissue removed. The pathologist inks the outer surfaces of the specimen and examines under the microscope whether dysplastic cells reach any edge.

Negative (clear) margin — No dysplasia at the cut edges. The visible abnormal area appears to have been removed completely.
Positive (involved) margin — Dysplasia extends to a cut edge, meaning abnormal tissue likely remains. Depending on the grade and the site, the team may consider removing more tissue or may opt for closer monitoring.
Cannot be assessed — The tissue was fragmented, or the edges were cauterized during removal, so the margin cannot be evaluated reliably. This is common with laser excision and does not mean the procedure was inadequate, but it makes careful follow-up more important.

Margins in dysplasia are interpreted differently from margins in cancer surgery. Dysplasia often extends beyond what can be seen in the mouth, and the surrounding lining may already carry genetic damage while looking entirely normal under the microscope. A negative margin therefore means the abnormal-looking tissue was removed, not that the risk has been eliminated. Studies have found that achieving clear margins does not reliably prevent a new lesion or a cancer from developing at the same site, which is why surveillance continues after excision regardless of what the margins show. Reports may also note whether hyperkeratosis alone reaches a margin; this carries less weight than dysplasia at a margin.

What is the risk that keratinizing squamous dysplasia will turn into cancer?

This is the question most people want answered, and it deserves specific figures rather than reassurance. Keratinizing squamous dysplasia is a precancerous change in the lining of the mouth, and most people who have it never develop cancer. Across pooled studies of oral epithelial dysplasia, roughly 12% of patients went on to develop oral squamous cell carcinoma, with a reported range of about 8% to 18%. Put the other way, close to nine out of ten did not. When cancer does develop, the average interval is around four years, and the risk is highest in the first two years after diagnosis, so this is a risk that regular follow-up is well suited to catch.

Risk rises with grade. In a recent meta-analysis of white patches in the mouth, the proportion that progressed to cancer was about 7% for mild dysplasia, 11% for moderate dysplasia, and 17% for severe dysplasia, compared with about 2% for patches showing no dysplasia at all. Expressed as an annual rate, published figures are roughly 1.7% per year for mild dysplasia and 3.6% per year for severe dysplasia. In several studies the difference between mild and moderate was not statistically significant, while severe dysplasia stood clearly apart. Note that even mild dysplasia carries real risk, which is why no grade is simply dismissed.

Factors that increase risk include:

Higher grade — Severe or high-grade dysplasia carries the clearest increase in risk.
Location — Lesions on the side or undersurface of the tongue and on the floor of the mouth carry higher risk than lesions elsewhere.
Appearance — Patches with mixed red and white areas or an uneven surface carry higher risk than uniform white patches. Red patches carry the highest risk.
Size — Larger lesions, generally those over 2 cm, are associated with higher risk.
Multiple or recurring lesions — Dysplasia at more than one site, or returning after removal, indicates a higher-risk situation.
Continued tobacco and alcohol use — Ongoing exposure continues the damage that produced the dysplasia. This is the one risk factor that can be changed.

These figures are averages drawn from groups of patients followed over many years in studies using differing definitions and populations. They describe patterns rather than predictions for any one person, and your own risk is best discussed with the clinician who can see your lesion and knows your history.

What happens after the diagnosis?

Once keratinizing squamous dysplasia has been confirmed on biopsy, next steps depend on the grade, the size and location of the area, its appearance, and your risk factors. The pathology report informs these decisions but does not determine them on its own, and practice genuinely varies because the evidence does not point to one clearly superior approach. Care is usually shared between an oral and maxillofacial surgeon, an ear nose and throat surgeon, an oral medicine specialist, and your dentist.

Two approaches are considered, often in combination:

Complete removal — The area is excised with a scalpel or a laser. This is considered more often for severe or high-grade dysplasia, for lesions on the tongue or floor of the mouth, and for red or mixed red-white patches. Removal serves two purposes: it takes out the abnormal tissue, and it allows the whole area to be examined, which sometimes reveals a higher grade or an unsuspected early cancer the biopsy missed.
Surveillance — The area is monitored with regular examination and photography, with repeat biopsy if it changes. This is considered more often for mild or low-grade dysplasia, for large or multifocal areas where removal would cause meaningful functional problems, and for lower-risk locations.

It is worth being clear about what removal does and does not achieve. Excision reduces the risk of cancer developing at that site, and in one large series patients whose high-grade dysplasia was removed developed cancer at roughly half the rate of those who were not treated. However, removal does not eliminate risk. Dysplasia recurs at the same site in roughly a quarter to a third of cases, and cancer can still develop in tissue that looked normal. Surveillance therefore continues after excision rather than replacing it.

Alongside either approach, two things consistently matter. The first is stopping tobacco and reducing alcohol, which removes the ongoing damage driving the process and is the most effective step available to most patients. Some lower-grade lesions improve or resolve once these exposures stop. Support for quitting is a standard part of care and worth asking for. The second is regular examination of the entire mouth, not only the treated area, typically every three to six months at first and less often over time if things remain stable. Because of field change, follow-up looks for new lesions elsewhere as well as recurrence at the original site, and it generally continues for many years rather than a fixed period.

Questions to ask your doctor

What grade of dysplasia was found, and did my report use the mild-moderate-severe system or the low-grade and high-grade system?
If my report says moderate dysplasia, is that being treated as lower risk or higher risk in my case?
Where exactly in my mouth is the abnormal area, and how large is it?
Does the location or appearance of my lesion put me at higher risk?
Was there any question of this being a reactive change from friction, yeast infection, or inflammation rather than true dysplasia?
Was the whole area removed, or only a sample taken?
If the area was removed, were the margins clear, and what does that mean for my risk?
Given my grade and my risk factors, what is my estimated risk of developing oral cancer?
Should this area be removed, or can it be safely monitored, and what are the trade-offs?
If we monitor it, how often will I be examined, and what changes would prompt another biopsy?
How long will follow-up continue, and will the rest of my mouth be examined each time?
What help is available to me for stopping tobacco or reducing alcohol?
Should my report be reviewed by a pathologist who specializes in oral or head and neck pathology?
What changes in my mouth should prompt me to call before my next scheduled visit?