Section Editor: Allison Osmond MD FRCPC
June 13, 2026
Bowen’s disease is another name for squamous cell carcinoma in situ of the skin, a very early form of skin cancer. It begins in squamous cells, the flat cells that make up the outer layer of the skin, called the epidermis. In Bowen’s disease, the cancer cells are still confined to the epidermis and have not grown into the deeper layers, which is why it is also called noninvasive squamous cell carcinoma.
This article explains what a diagnosis of Bowen’s disease means, what the findings in your pathology report describe, and how those findings guide the decisions you and your doctor make together. Bowen’s disease is one of the most treatable forms of skin cancer, and when it is found and treated early, it is usually cured. If it is left untreated, it can, over time, progress into invasive squamous cell carcinoma, which can grow into deeper tissue and, occasionally, spread to other parts of the body.
Is Bowen’s disease benign or malignant?
Bowen’s disease is made up of malignant (cancerous) cells. However, because those cells are confined to the epidermis and cannot yet reach blood vessels or lymphatic channels, they are unable to spread elsewhere in the body at this stage. For that reason, when Bowen’s disease is found and treated early, it behaves much like a benign condition and is usually curable.
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 light, such as tanning beds, can also increase the risk. Other contributing factors include a weakened immune system (for example, from anti-rejection medication after an organ transplant or from HIV), infection with human papillomavirus (HPV) (especially for Bowen’s disease in the genital area), and long-standing skin injury or inflammation, such as from old burns or scars.
What are the symptoms of Bowen’s disease?
Bowen’s disease usually appears as a slowly growing, red, scaly patch of skin. The patch may feel rough and may be itchy or tender. It develops most often on sun-exposed areas such as the face, neck, hands, and lower legs, but it can also appear in areas with less sun exposure, including the genital region. Because it can look like eczema, psoriasis, or a fungal infection, a biopsy is often needed to confirm the diagnosis.
How is the diagnosis made?
The diagnosis is usually made after a biopsy, in which a small piece of the patch is removed and examined under the microscope by a pathologist. Under the microscope, the normal, orderly squamous cells of the epidermis are replaced from the surface downward by abnormal cells, but these abnormal cells remain within the epidermis and do not invade the dermis (the layer beneath it). The abnormal cells are large, hyperchromatic (darker than normal), and pleomorphic (varying in size and shape), and they include scattered dyskeratotic cells (dying squamous cells) and numerous mitotic figures (dividing cells). Examining the tissue also allows the pathologist to rule out conditions that may appear similar, such as psoriasis or dermatitis. If the patch is large, your doctor may recommend removing the whole area so the pathologist can check that the disease has not already become invasive.
What is the risk of developing invasive squamous cell carcinoma?
If Bowen’s disease is left untreated, it can progress into invasive squamous cell carcinoma. Research suggests this occurs in roughly 3-10% of cases. The risk is higher in people who:
- Have a weakened immune system — Such as transplant recipients or people with HIV.
- Have lesions on the lips, ears, or genitals — Tumors in these areas carry a higher risk of becoming invasive.
- Have large or long-standing lesions — Especially when they have gone untreated for a long time.
Because invasive squamous cell carcinoma can be more serious and harder to treat, early treatment of Bowen’s disease is recommended.
Surgical margins
A margin is the edge of the tissue removed during surgery. When the goal of the procedure is to remove the entire lesion, the pathologist examines the margins to determine whether abnormal cells extend to the cut edge. This tells you and your doctor whether the entire lesion was removed.
- Negative margin — No abnormal cells are seen at the cut edge, which suggests the lesion was completely removed (sometimes described as “completely excised”). The report may also give the distance from the abnormal cells to the nearest edge, and a greater distance offers more reassurance.
- Positive margin — Abnormal cells are present at the cut edge, which means some of the lesion may remain (sometimes described as “incompletely excised”). This is common after a small biopsy intended only to make the diagnosis, but when the goal was to treat the lesion, a positive margin may require another procedure to remove the remaining tissue.
What happens after this diagnosis?
Because Bowen’s disease is confined to the skin’s surface, it can be treated in several ways, and the best choice depends on the size and location of the lesion, the number of lesions, and your overall health. Options that your doctor may consider include surgical removal (excision), Mohs micrographic surgery for lesions in cosmetically sensitive or high-risk areas such as the face, curettage and electrodesiccation (scraping and heat), cryotherapy (freezing), topical creams that treat the skin over several weeks (such as 5-fluorouracil or imiquimod), and photodynamic therapy (a light-activated treatment). Radiation therapy is used in selected situations, particularly for people who are not candidates for surgery.
After treatment, regular skin checks are recommended, both to make sure the lesion has not come back and because people who have had Bowen’s disease often have sun-damaged skin and are at higher risk of developing other skin cancers. Protecting the skin from further sun exposure is an important part of long-term care. Your doctor can advise how often you should be examined based on your individual risk.
Questions to ask your doctor
- Was my lesion completely removed, and were the margins negative?
- If the margins were positive, do I need another procedure?
- What is my risk of this turning into invasive squamous cell carcinoma?
- Which treatment option is best for my lesion (excision, Mohs surgery, cryotherapy, topical therapy, or photodynamic therapy)?
- Was there any sign that the disease had already become invasive?
- How will I know if the disease has come back?
- How often should I have follow-up skin checks?
- Am I at higher risk of developing other skin cancers?
- What can I do to protect my skin from further sun damage?
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