AKT · Dermatology/Malignant & pre-malignantlow yield

Bowen disease

Squamous cell carcinoma IN SITU (intraepidermal)

Overview

Squamous cell carcinoma in situ — full-thickness epidermal dysplasia that has not yet breached the basement membrane. A slowly enlarging, well-demarcated, erythematous SCALY plaque, classically on the lower legs of older women. A small proportion progress to invasive SCC.

Recognise

A slowly enlarging, well-demarcated, erythematous scaly or crusted plaque, often on the lower leg
Flat (does not have the rolled edge of BCC or the nodularity of invasive SCC)
Risk factors: chronic sun exposure, older age, immunosuppression, HPV, prior arsenic exposure

Red flags

Development of a nodule, ulceration, or rapid growth within the plaque → progression to invasive SCC (biopsy)

Differentials & how to tell them apart

Superficial BCCthread-like pearly rolled border, often on the trunk

Psoriasis/eczema (a single plaque)responds to topical steroid, usually multiple/symmetrical — a solitary persistent scaly plaque that resists treatment should be biopsied

Invasive SCCnodular/indurated/ulcerated — Bowen is flat and in-situ

Actinic keratosissmaller, rough, ill-defined macule — Bowen is a larger well-defined plaque (full-thickness dysplasia)

Clinical image

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Bowen disease — clinical imagesDermNet

Investigations

Dermoscopy + biopsy (full-thickness epidermal atypia, intact basement membrane). Biopsy any nodular/ulcerated area to exclude invasive SCC.

Management

Topical 5-fluorouracil or imiquimod, cryotherapy, or PDT for the in-situ plaque

1Confirm with biopsy. Treat the in-situ plaque with topical 5-FU or imiquimod, cryotherapy, curettage or photodynamic therapy.Gate: A new nodule, induration or ulceration within a Bowen plaque signals progression to INVASIVE SCC → biopsy and excise rather than continuing topical field therapy
2Unresponsive, nodular, or diagnostically uncertain → surgical excision; surveillance for further keratinocyte cancers.

Topical 5-fluorouracil or imiquimod — common first-line for the in-situ plaque

Cryotherapy / curettage / photodynamic therapy — alternatives for suitable lesions

Surgical excision — for diagnostic uncertainty, nodular change, or unresponsive disease

Key points

Bowen = SCC in situ; only a minority become invasive but a changing nodule must be biopsied. Lower legs of older women is the classic location (slow healing — choose treatment accordingly).

Monitor & prognosis

Response to field therapy; watch for invasive change.

Excellent; small risk of progression to invasive SCC.

Source: NICE CKS; BAD Bowen disease guideline