by Jason Wasserman MD PhD FRCPC and Zuzanna Gorski MD
April 10, 2026
Keratinizing squamous dysplasia is a precancerous condition affecting the lining of the oral cavity. It develops in squamous cells — the flat cells that normally form the surface layer of the mouth’s lining — when they start to grow and mature abnormally. One of its defining features is the excess production of keratin, a tough protein normally found in skin, hair, and nails. When too much keratin is produced inside the mouth, the lining thickens, and the abnormal area may appear as a white, red, or mixed white-and-red patch on the surface of the mouth.
Keratinizing squamous dysplasia is not cancer, but it is a serious precancerous condition because the abnormal cells have the potential to progress to squamous cell carcinoma — a type of oral cavity cancer — if left untreated or not carefully monitored. A biopsy is performed to confirm the diagnosis and determine the grade of dysplasia, which guides treatment and follow-up decisions. Identifying and treating this condition early is important because it gives the best chance of preventing cancer from developing.
Where does keratinizing squamous dysplasia occur?
Keratinizing squamous dysplasia can develop anywhere in the oral cavity that is lined by squamous epithelium. It most commonly affects areas that are frequently exposed to irritants such as tobacco smoke or alcohol. These include the sides and underside of the tongue, the floor of the mouth, the inner lining of the cheeks, the gums, the hard palate, and the inner surface of the lips.
What causes keratinizing squamous dysplasia?
Keratinizing squamous dysplasia results from chronic damage to the cells lining the oral cavity. Several factors are known to increase the risk:
- Tobacco use. This is the most important modifiable risk factor. Cigarettes, cigars, pipes, and smokeless tobacco all significantly increase the risk of dysplasia and oral cavity cancer.
- Alcohol use. Alcohol independently increases risk and is especially harmful when combined with tobacco, because it makes the oral lining more permeable to carcinogens in tobacco smoke.
- Betel (areca) nut chewing. In parts of South and Southeast Asia, betel nut chewing is a major cause of oral dysplasia and cancer. Betel nut contains compounds that directly damage oral mucosal cells.
- Chronic inflammation and irritation. Conditions such as oral lichen planus and long-standing mechanical irritation from poorly fitting dental appliances can contribute to dysplasia over time.
- Immune suppression. People taking immunosuppressive medications — such as those who have had an organ transplant — are at significantly higher risk because their immune systems are less able to detect and eliminate abnormal cells.
Importantly, keratinizing squamous dysplasia is a separate condition from HPV-associated dysplasia of the oral cavity. The two conditions look different under the microscope, have different causes, and are managed somewhat differently. If your biopsy shows keratinizing dysplasia, HPV is not the cause.
What are the symptoms?
Many people with keratinizing squamous dysplasia have no noticeable symptoms, particularly in the early stages. The condition is often detected during a routine dental examination. When symptoms do occur, they typically develop gradually and may include:
- Persistent white patches (leukoplakia) — the most common presentation.
- Red patches (erythroplakia) or mixed red-and-white patches — these carry a higher risk of underlying dysplasia than white patches alone.
- Areas of the mouth lining that feel thicker, rougher, or firmer than the surrounding tissue.
- Pain, tenderness, or a burning sensation, especially when eating spicy, acidic, or hot foods.
- In more extensive cases, difficulty chewing, swallowing, or speaking.
Any patch or sore in the mouth that persists for more than two to three weeks should be evaluated by a dentist or doctor.
How is the diagnosis made?
The diagnosis is made by a pathologist who examines a tissue sample under the microscope. When a doctor or dentist finds an abnormal area in the mouth, a biopsy is taken — a small sample of tissue is removed from the abnormal area and sent to the pathology laboratory. The pathologist evaluates how abnormal the squamous cells appear, how much keratin they produce, and how deeply the abnormal cells extend into the surface lining of the mouth. Based on these features, the pathologist assigns a grade to the dysplasia.
What does the pathology report describe?
Microscopic features
Under the microscope, keratinizing squamous dysplasia shows a range of abnormal changes in the squamous cells and their organization. The extent of these changes determines the grade. Features the pathologist may describe include:
- Excess keratinization. The epithelial surface produces more keratin than normal, appearing thickened and sometimes forming a rough or scaly layer. This is the hallmark feature that gives the condition its name.
- Atypia. The squamous cells look abnormal — they may vary in size and shape (pleomorphism), have enlarged or irregularly shaped nuclei, and appear darker than normal (hyperchromatic nuclei). These changes reflect the abnormal growth program the cells have acquired.
- Increased mitotic figures. More cells than usual are in the process of dividing, a finding called increased mitotic activity. In dysplasia, dividing cells may also be found in abnormal locations — higher up in the epithelial layer than they should be.
- Disrupted cell organization. Normally, squamous cells in the oral lining are arranged in an orderly layered pattern. In dysplasia, this architecture is disturbed. The degree of disruption — how much of the full thickness of the lining is affected — is one of the key features used to determine the grade.
Grade
The grade of keratinizing squamous dysplasia reflects the severity of cell abnormality and the extent of the affected lining. The grade is the most important piece of information in the pathology report because it directly guides treatment decisions.
Mild keratinizing squamous dysplasia
Abnormal cells are limited to the lower third of the epithelium. The cells show mild abnormalities that are only slightly different from normal. The risk of progression to cancer is relatively low. Careful monitoring with regular follow-up examinations — rather than surgery — is usually recommended, along with elimination of risk factors such as tobacco and alcohol.
Moderate keratinizing squamous dysplasia
Abnormal cells extend into the middle third of the epithelium. The cellular abnormalities are more pronounced. This grade carries a higher risk of progression than mild dysplasia. Management may involve surgical removal of the abnormal tissue or closer surveillance, depending on the patient’s overall clinical situation and risk factors.
Severe keratinizing squamous dysplasia
Abnormal cells involve more than two-thirds of the epithelium but do not yet extend through its full thickness. The cellular abnormalities are marked and close to those seen in carcinoma. This grade is associated with a significant risk of progression to squamous cell carcinoma, and surgical removal of the affected area is generally recommended.
It is important to know that severe keratinizing squamous dysplasia is also sometimes called squamous cell carcinoma in situ. These two terms describe the same degree of cellular change. Despite the word “carcinoma” in that alternate name, it is not invasive cancer — the abnormal cells are still confined within the surface lining of the mouth and have not yet broken through into the deeper tissue. If you see “squamous cell carcinoma in situ” on your report, it is describing the same finding as severe dysplasia.
Margin
When the abnormal area is surgically removed, the pathologist examines the margin — the edge of the tissue that was cut — to determine whether the entire area of dysplasia was taken out.
- Negative margin (clear margin). No dysplasia is found at the cut edge. This means the abnormal area appears to have been completely removed.
- Positive margin. Dysplastic cells are present at the cut edge, suggesting some abnormal tissue may remain. Your doctor will discuss whether additional treatment is needed.
- Cannot be assessed. If the tissue was fragmented or cauterized at the edges during removal, the margin may not be reliably evaluable. In this case, close follow-up is especially important.
What is the risk of developing cancer?
Keratinizing squamous dysplasia is not cancer, but it carries a real risk of progressing to oral cavity squamous cell carcinoma over time if left untreated. The risk increases with higher grades:
- Mild dysplasia carries the lowest risk. Some cases of mild dysplasia regress or stabilize, particularly when risk factors such as smoking are eliminated.
- Moderate dysplasia carries an intermediate risk and warrants closer follow-up and often treatment.
- Severe dysplasia carries the highest risk and typically requires surgical removal. If left untreated, severe dysplasia has a substantial probability of progressing to invasive cancer over a period of years.
Continuing to use tobacco and alcohol significantly increases the risk of progression at all grades. Addressing these risk factors is one of the most important things a patient can do to reduce their risk of cancer.
What happens next?
Management depends primarily on the grade of dysplasia and the patient’s individual risk factors.
- Mild dysplasia. Close monitoring is typically the first approach. Regular follow-up examinations — usually every 3 to 6 months initially — allow the doctor to monitor for any changes. Eliminating tobacco and alcohol use is strongly recommended, as these changes alone can sometimes lead to improvement.
- Moderate dysplasia. Surgical excision is often recommended, particularly when risk factors such as tobacco use are present or when the lesion shows features that raise concern for progression. If excision is not immediately performed, more frequent surveillance is needed.
- Severe dysplasia (squamous cell carcinoma in situ). Surgical excision is the standard treatment. The goal is to remove the entire area of dysplasia with clear margins. After excision, regular follow-up is still required because new dysplastic lesions can develop elsewhere in the oral cavity, particularly in people who continue to use tobacco or alcohol.
Regardless of grade, quitting smoking and reducing alcohol intake are the most impactful lifestyle changes a patient can make. These steps reduce the risk of progression and of developing new lesions in other parts of the mouth.
After excision, follow-up appointments — typically every three to six months for the first year or two, then annually — allow the surgeon or dentist to monitor the treated site and examine the rest of the oral cavity. Additional biopsies may be taken if new or changing areas are identified.
Questions to ask your doctor
- What grade of dysplasia was found, and what does that mean for my risk?
- Was the entire abnormal area removed, and what did the margins show?
- Do you recommend surgery, monitoring, or both?
- How often do I need follow-up exams, and what will those involve?
- Will I need additional biopsies in the future?
- How much does quitting smoking or reducing alcohol consumption reduce my risk?
- Is this related to HPV, or is it a different type of dysplasia?
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