Your pathology report for Bowen’s disease

by Jason Wasserman MD PhD FRCPC
September 13, 2025

Bowen’s disease is another name for squamous cell carcinoma in situ, an early form of skin cancer. It begins in squamous cells, which are the flat cells that comprise the outermost layer of the skin, known as the epidermis.

Normal skin histology

At this stage, the cancer cells are confined to the epidermis and have not spread deeper into the skin. This is why Bowen’s disease is sometimes described as non-invasive squamous cell carcinoma.

If left untreated, Bowen’s disease can progress into invasive squamous cell carcinoma, which can spread deeper into the skin and occasionally to other parts of the body.

What are the symptoms of Bowen’s disease?

Bowen’s disease usually appears as a slow-growing, red, scaly patch of skin. The patch may feel rough, itchy, or tender to the touch.

It most often develops on sun-exposed parts of the body, such as the:

  • Face.

  • Neck.

  • Hands.

  • Lower legs.

However, Bowen’s disease can also appear in less sun-exposed areas, including the genital region. Because it can resemble eczema, psoriasis, or fungal infections, a biopsy is often necessary to confirm the diagnosis.

What causes Bowen’s disease?

The most common cause of Bowen’s disease is long-term exposure to ultraviolet (UV) radiation, usually from the sun. Artificial sources of UV radiation, such as tanning beds, can also increase risk.

Other factors that may contribute include:

  • Weakened immune system, such as from medications after an organ transplant or conditions like HIV/AIDS.

  • Human papillomavirus (HPV) infection, especially in genital Bowen’s disease.

  • Chronic skin injury or inflammation, such as from burns or scars.

Is Bowen’s disease benign or malignant?

Bowen’s disease is made up of malignant (cancerous) cells, but because these cells are confined to the epidermis, they cannot spread elsewhere in the body at this stage.

When detected and treated early, Bowen’s disease behaves more like a benign condition and is usually curable.

How is this diagnosis made?

The diagnosis of Bowen’s disease is usually made after a biopsy. During this procedure, a small piece of the skin lesion is removed and examined under a microscope by a pathologist.

Under the microscope, the pathologist looks for abnormal squamous cells confined to the epidermis. The biopsy also rules out other conditions that can mimic Bowen’s disease, such as psoriasis or dermatitis.

If the lesion is large, your doctor may recommend removing the entire area to check for signs that the disease has progressed into invasive squamous cell carcinoma.

What does Bowen’s disease look like under the microscope?

When viewed under the microscope, Bowen’s disease shows:

What is the risk of developing invasive squamous cell carcinoma?

If left untreated, Bowen’s disease can progress into invasive squamous cell carcinoma. Research suggests that this occurs in approximately 3–10% of cases.

The risk is higher in people who:

  • Have a weakened immune system.

  • Have lesions on the lips, ears, or genitals, which tend to behave more aggressively.

  • Have large or long-standing lesions that are left untreated.

Because invasive squamous cell carcinoma can be more serious, early treatment of Bowen’s disease is strongly recommended.

What are margins, and why are they important?

A margin is the edge of the tissue removed during surgery. Pathologists carefully examine the margins to see whether tumour cells are present.

  • A negative margin means no cancer cells are seen at the edge, suggesting the lesion has been entirely removed.

  • A positive margin means that cancer cells are visible at the edge, suggesting that some may remain in the body.

Sometimes, reports also include the distance between the cancer cells and the nearest margin. A greater distance provides more reassurance that the disease has been entirely removed.

What does completely excised mean?

Completely excised means that the entire lesion was removed during surgery. Pathologists check the margins (the edges of the removed tissue) to confirm that no cancer cells are present at the outer edge.

What does incompletely excised mean?

Incompletely excised means that cancer cells are still seen at the tissue margin, suggesting that part of the lesion remains.

This can occur after a biopsy, which is often intended to confirm the diagnosis rather than remove the entire lesion. However, when the goal is to treat the lesion with surgery, doctors aim for complete excision. If the disease is incompletely excised, another procedure may be recommended.

Questions to ask your doctor

  • Was my lesion completely removed, and were the margins negative?

  • What is my risk of this turning into invasive squamous cell carcinoma?

  • What treatment options are available (excision, cryotherapy, topical therapy, photodynamic therapy)?

  • How will I know if the disease has come back?

  • How often should I have follow-up skin checks after this diagnosis?

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