Bowen’s disease is considered an early, non-invasive form of skin cancer, also known as Squamous Cell Carcinoma in situ. This condition involves the abnormal growth of cells in the outermost layer of the skin. Though slow-growing and highly treatable, it is classified within the cancer spectrum. Early recognition and treatment are important steps in preventing its progression into a more concerning, invasive form of skin cancer.
Defining the Classification
Bowen’s disease is medically classified as Squamous Cell Carcinoma in situ (SCCis). This classification means the abnormal, potentially malignant cells originate from keratinocyte cells, the main cell type in the epidermis. The term in situ signifies that the cancerous growth is entirely contained within the epidermis, the top layer of the skin.
This containment distinguishes Bowen’s disease from invasive squamous cell carcinoma. The epidermis is separated from the deeper layer of skin, the dermis, by the basement membrane. In Bowen’s disease, the abnormal cells have not yet breached this crucial boundary, meaning they cannot spread to deeper tissues or other parts of the body.
Because the cells are non-invasive and localized, Bowen’s disease is sometimes referred to as a pre-invasive or Stage 0 skin cancer. If left untreated, there is a 3 to 5% risk that the malignant cells will penetrate the basement membrane and become an invasive squamous cell carcinoma. The integrity of this membrane separates SCCis from a more serious, metastatic cancer.
Identifying Symptoms and Appearance
Bowen’s disease typically presents as a single, slow-growing patch on the skin that does not heal. This lesion often appears as a persistent, reddish-brown or red patch with defined edges. The surface is usually scaly, crusty, or slightly raised, sometimes resembling eczema or psoriasis.
Patches can range in size from a few millimeters to several centimeters across and may occasionally be itchy. While most people develop only one lesion, 10 to 20% of affected individuals may develop multiple patches. The disease can occur anywhere on the body, but it is most common on sun-exposed sites like the head, neck, lower legs, and hands.
In non-sun-exposed areas, such as the genital or anal regions, a form called Bowenoid papulosis may present as brown or dark brown patches. The condition may also affect mucous membranes, such as the mouth. Changes in the patch, including bleeding, the formation of an open sore, or the development of a lump, can signal progression to invasive cancer.
Primary Causes and Risk Factors
The development of Bowen’s disease is strongly linked to cumulative, long-term exposure to environmental and biological factors. Chronic ultraviolet (UV) radiation is the primary cause, stemming from years of sun exposure or tanning bed use. This UV damage causes genetic changes in skin cells, making them susceptible to becoming cancerous.
Infection with certain strains of Human Papillomavirus (HPV) is a recognized risk factor, especially in cases on non-sun-exposed skin like the genital area. Specific strains, notably HPV-16, are implicated in driving the cell changes. Individuals with a compromised immune system, such as those taking immunosuppressant medications, also face a heightened risk.
A less common cause is long-term exposure to arsenic, which may occur through contaminated well water or occupational exposure. The condition is also more prevalent in older adults and individuals with fair skin, reflecting the cumulative nature of the primary risk factors.
Treatment Approaches and Monitoring
The goal of treating Bowen’s disease is to completely remove or destroy the localized abnormal cells. Surgical excision is a common approach where the lesion is cut out under local anesthesia and closed with stitches. This method provides a tissue sample for laboratory confirmation that the margins are clear of cancer cells.
Non-surgical approaches are often preferred for larger or multiple lesions, or in areas where scarring is a concern. Cryotherapy involves freezing the patch with liquid nitrogen, which destroys the abnormal cells and leads to healing. Topical chemotherapy creams (e.g., 5-fluorouracil) or immune-response modifiers (e.g., imiquimod) can be applied directly to the lesion over several weeks to destroy the cancer cells.
Photodynamic Therapy (PDT) involves applying a light-sensitizing cream to the patch, followed by exposure to a specific wavelength of light to kill the abnormal cells. Following successful treatment, long-term monitoring is important, typically involving follow-up appointments every 6 to 12 months. This monitoring addresses the risk of recurrence or new lesions developing. Patients should also perform regular self-examinations and continue rigorous sun protection to minimize future skin damage.