Actinic cheilitis: Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
March 2, 2026

Actinic cheilitis is a precancerous condition that affects the lips, most commonly the lower lip. It develops after many years of exposure to ultraviolet (UV) radiation, usually from sunlight.

The lips are covered by a thin layer of skin and mucosa that is more sensitive to sun damage than other areas of the body. Over time, repeated sun exposure can damage the DNA inside the cells of this surface layer, causing the cells to grow and mature abnormally.

Actinic cheilitis is not cancer, but it is important because it can develop into squamous cell carcinoma, a type of skin cancer, if left untreated. Early detection and treatment significantly reduce this risk.

What does actinic cheilitis look like?

Actinic cheilitis most often affects the lower lip because it receives more direct sun exposure than the upper lip.

The affected area may appear dry, rough, scaly, or cracked. The lip may look pale, blotchy, or slightly thickened. Some areas may feel tender or sensitive. In more advanced cases, small ulcers or persistent sores may develop.

These changes usually develop gradually over time.

What causes actinic cheilitis?

The primary cause of actinic cheilitis is long-term exposure to ultraviolet radiation from the sun. Artificial sources of UV radiation, such as tanning beds, can also contribute.

People with lighter skin tones are at higher risk because they have less natural melanin protection against UV radiation. Other risk factors include outdoor occupations, a history of significant sun exposure, and older age.

Repeated sun damage leads to genetic changes in the cells lining the lip, causing them to grow abnormally.

How is this diagnosis made?

The diagnosis of actinic cheilitis is often suspected based on the appearance of the lips during a physical examination.

If the lesion has concerning features, such as thickening, ulceration, or persistent non-healing, a biopsy may be performed. During a biopsy, a small piece of tissue is removed and examined under a microscope by a pathologist.

The microscopic examination confirms the diagnosis and helps rule out invasive squamous cell carcinoma.

Microscopic features

Under the microscope, actinic cheilitis shows changes in both the surface lining (epithelium) and the underlying connective tissue.

The epithelium may appear thicker in some areas or thinner in others. The cells often show atypia, meaning they look abnormal in size, shape, and organization. The normal orderly maturation of cells from the bottom layer to the surface may be disrupted. These changes are similar to those seen in squamous dysplasia and represent precancerous activity.

The surface layer often shows increased keratin production, the protein that makes skin tough and protective. This explains the rough, scaly appearance seen clinically.

In the underlying connective tissue, a characteristic change called solar elastosis is often present. Solar elastosis refers to the accumulation of abnormal elastic fibers caused by chronic sun damage. This gives the tissue a dense, disorganized appearance under the microscope.

These findings help distinguish actinic cheilitis from other inflammatory or pigmented conditions of the lip.

What is the risk of developing cancer?

Actinic cheilitis carries a risk of developing into squamous cell carcinoma of the lip. The risk varies with the severity of cellular changes and ongoing sun exposure.

Thicker areas, ulcerated lesions, or areas showing more severe dysplasia are at higher risk of progression. Early treatment and sun protection significantly reduce this risk.

Margins

A margin refers to the edge of the tissue removed during a biopsy or excision.

When a biopsy is performed, only a small portion of the lesion is removed. If abnormal cells are present at the edges of the biopsy sample, this may suggest that additional abnormal tissue remains in the lip.

When the entire lesion is removed in a procedure called an excision, the margins are carefully examined under the microscope.

A negative margin means that no abnormal cells are seen at the edge of the removed tissue. This suggests that the actinic cheilitis has been completely removed.

A positive margin means that abnormal cells are present at the edge of the tissue. This indicates that some precancerous tissue may remain and that additional treatment or closer follow-up may be needed.

Questions you may want to ask your doctor

• Does my biopsy show mild or more severe dysplasia?

• Was all of the abnormal tissue removed?

• What is my risk of developing squamous cell carcinoma?

• How often should my lips be examined?

• What steps can I take to protect my lips from further sun damage?