Keratosis

Keratosis is a word pathologists use to describe an increased amount of keratin on the surface of squamous epithelium, the type of tissue that lines the skin, mouth, throat, esophagus, anus, cervix, and other body surfaces. Keratin is a tough, protective protein made by squamous cells. It forms the outermost layer of the skin and helps protect the body from injury, infection, and dehydration.

When the body produces more keratin than usual, the result is called keratosis. This change is usually a benign (non-cancerous) response to irritation or inflammation, although it can also be seen in precancerous or cancerous conditions, depending on the surrounding tissue and context.

What causes keratosis?

Keratosis can develop as a normal response to repeated friction, irritation, or inflammation. It is commonly seen in areas exposed to chronic stress, such as the skin of the hands or feet, or mucosal surfaces affected by smoking, infection, or acid reflux.

Common causes include:

• Chronic rubbing or pressure (as with calluses or corns on the skin).

• Inflammatory conditions, such as eczema, psoriasis, or lichen planus.

• Irritants, including tobacco smoke, poorly fitting dentures, or acid reflux.

• Precancerous changes, such as in actinic keratosis on sun-damaged skin.

• Early surface change in squamous cell carcinoma, a type of cancer.

What are the types of keratosis?

There are different types of keratosis, depending on how the keratin builds up:

• Hyperkeratosis – A general term for thickened keratin on the surface of the epithelium. This is often seen in response to chronic irritation and is not cancerous.

• Parakeratosis – A form of keratosis where the surface layer contains nuclei that are usually lost as cells mature. Parakeratosis is often seen in inflamed or regenerating tissue.

• Orthokeratosis – A type of hyperkeratosis where the surface keratin is thickened but lacks nuclei, which is normal for mature keratin.

• Actinic keratosis – A precancerous lesion caused by long-term sun exposure, often seen on the face, scalp, and hands. It can sometimes progress to squamous cell carcinoma.

Your pathology report may include one or more of these terms depending on the type and cause of keratosis observed.

Is keratosis serious?

Keratosis by itself is not usually serious, especially when seen as a reactive change in response to irritation or injury. It often goes away once the source of irritation is removed.

However, in some cases, keratosis may be a sign of underlying dysplasia (precancerous changes) or cancer, especially if it occurs alongside abnormal cell growth or in a high-risk area, such as the cervix or oral cavity in people with a history of tobacco use.

Your doctor will consider your overall health, risk factors, and other findings in the pathology report to determine whether treatment or follow-up is needed.

What does keratosis look like under the microscope?

Under the microscope, keratosis appears as a thickened surface layer of keratin on top of squamous epithelium.

The exact appearance depends on the type:

• Hyperkeratosis looks like a thick, compact pink surface layer.

• Parakeratosis shows flattened cells with retained nuclei in the surface keratin.

• Orthokeratosis shows a smooth surface layer without nuclei, typical of mature keratin.

These findings help pathologists understand whether the tissue is reacting to irritation, inflammation, or something more concerning.

Questions to ask your doctor

• What type of keratosis was found in my report?

• Is this a benign (non-cancerous) change, or is further testing needed?

• What caused the keratosis in my case?

• Do I need treatment or follow-up monitoring?