Bowen's Disease (SCC In Situ) ICD-10: D04.9

Precancerous / Skin cancer in situ

Often searched as: scaly red patch on skin, red patch that won't go away, scaly skin that doesn't heal, flat red crusty spot on leg, slow growing skin patch, early skin cancer signs, precancerous skin patch, scaly patch on lower leg…

Clinical urgency level

lowmediumhigh

Systems Affected

skin (epidermis only — in situ)

Severity Levels

mild

Small, stable, well-defined scaly patch in a low-risk location — treatable with topical therapies (5-fluorouracil, imiquimod) or photodynamic therapy.

moderate

Larger lesion or multiple lesions, on the face or genitals, requiring more aggressive local treatment or surgical excision.

severe

Bowen's disease progressing to invasive SCC — deeper invasion confirmed by biopsy, requiring wider surgical excision and oncologic follow-up.

Red Flags

A scaly red patch that has been slowly growing for months or years
A patch that starts to thicken, become raised, or develop a nodular area within it (possible progression to invasive SCC)
Bleeding, ulceration, or crusting within the lesion
Bowen's disease on the penis (erythroplasia of Queyrat) or vulva — higher invasion risk
Rapidly growing area within a previously stable lesion
Multiple Bowen's lesions in an immunocompromised patient — higher risk of invasive transformation

Clinical Presentation

Bowen's disease — well-defined erythematous scaly plaque on the lower leg

Source: Wikimedia Commons (CC BY-SA 3.0 )

Bowen's disease image gallery — DermNet NZ

View gallery on DermNet NZ (image gallery reference)

When to See a Doctor

See a dermatologist if you have a persistent scaly red or pink patch that isn't going away — especially if it's been there for months and seems to be slowly growing. Bowen's disease is easily treated when caught early and confined to the surface. Any change in a known Bowen's lesion (thickening, bleeding, rapid growth) requires urgent re-evaluation.

Differential Diagnosis

Actinic keratosis (rougher, less defined — also SCC precursor)
Psoriasis (well-defined silvery plaques — often on elbows/knees)
Eczema / chronic dermatitis (itchy, oozing — different pattern)
Superficial basal cell carcinoma (may look similar — biopsy needed)
Tinea corporis (ringworm — circular, responds to antifungal)
Paget's disease of skin (eczema-like on nipple or genitals — different entity)

Comorbidities

Previous or concurrent actinic keratoses
HPV infection (especially HPV-16 — genital Bowen's)
Arsenic exposure (historical — multiple lesions on trunk)
Immunosuppression (organ transplant, HIV — higher risk and multiple lesions)
Other non-melanoma skin cancers
Internal malignancy (rare association with multiple truncal Bowen's — arsenic-related)

Prognosis

When treated appropriately while still in situ (confined to the epidermis), Bowen's disease has a near-100% cure rate. Untreated, approximately 3–5% of cases progress to invasive SCC over time, which carries a higher risk of metastasis. Treatment options include topical 5-fluorouracil, imiquimod, cryotherapy, photodynamic therapy (PDT), and surgical excision — all with good efficacy. PDT is preferred for large lesions on the lower legs. Regular follow-up is important as new lesions can develop, especially in high-UV-exposure individuals.

Detailed Overview

Causes, Symptoms, and When to Take Action Bowen's disease is a very early form of squamous cell skin cancer, also known as squamous cell carcinoma in situ. It is a slow-growing lesion confined to the epidermis — the outer layer of the skin. How It Looks Texture: Red, scaly patches that may appear flat or slightly raised Color: Usually red or pink; may appear brown or darker in pigmented skin tones Shape: Well-defined patches; occasionally raised spots or wart-like appearance Location: Commonly appears on sun-exposed areas such as the head, neck, trunk, arms, and legs Why Does It Appear? The exact cause of Bowen's disease isn't always known, but key contributors include prolonged exposure to ultraviolet radiation and weakened immunity. Other recognized factors include exposure to human papillomavirus (especially HPV-16), and, in rare cases, long-term exposure to arsenic. Should You Be Concerned? Yes. While typically slow-growing, Bowen's disease can progress into invasive squamous cell carcinoma if untreated. This invasive form can penetrate deeper into the skin and potentially spread. Regular monitoring and evaluation are, therefore, important. Can You Prevent It? You cannot always prevent Bowen's disease, but risk may be reduced by: Limiting UV exposure — especially consistent use of sun protection Monitoring the skin for new or changing patches Seeking prompt evaluation if any suspicious skin changes appear 👉 How Piel AI Can Help Piel AI enables you to track skin lesions over time using regular imaging. While it does not diagnose, it aids in detecting changes and supports discussions with healthcare providers. Summary Bowen's disease is squamous cell carcinoma in situ, appearing as red, scaly skin patches. It is slow-growing but may progress to invasive cancer if untreated. Causes include UV exposure, weakened immunity, HPV, and sometimes arsenic. Early evaluation and UV protection are key to managing risk.

Explore more conditions

Learn about other skin and hair conditions.

View all conditions →