Squamous Cell Carcinoma in Situ

(Bowen or Bowen's Disease; Intraepidermal Squamous Cell Carcinoma)

ByVinod E. Nambudiri, MD, MBA, EdM, Harvard Medical School
Reviewed/Revised Dec 2023
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Squamous cell carcinoma in situ is a superficial squamous cell neoplasm. Diagnosis is by biopsy. Treatment depends on the tumor’s characteristics and may involve curettage and electrodesiccation, surgical excision, topical chemotherapeutics, electrocautery, or cryosurgery.

(See also Overview of Skin Cancer.)

Squamous cell carcinoma in situ (formerly called Bowen disease) is most common in sun-exposed areas but may arise at any location.

Symptoms and Signs of Squamous Cell Carcinoma in Situ

Lesions can be solitary or multiple. They are red-brown and scaly or crusted, with little induration; they frequently resemble a localized thin plaque of psoriasis or dermatitis or a dermatophyte infection.

Squamous Cell Carcinoma in Situ (Shin)
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This photo shows a reddish-brown and scaly lesion consistent with squamous cell carcinoma in situ.
DR P. MARAZZI/SCIENCE PHOTO LIBRARY

Diagnosis of Squamous Cell Carcinoma in Situ

  • Biopsy

Squamous cell carcinoma in situ is often suspected when a rash secondary to a disorder such as psoriasis or atopic dermatitis fails to respond to treatment.

Diagnosis is by biopsy, which shows full-thickness epidermal dysplasia but no dermal involvement.

Treatment of Squamous Cell Carcinoma in Situ

  • Treatment with topical chemotherapeutics

  • Removal or ablation via local methods

Treatment of squamous cell carcinoma in situ depends on the lesion’s characteristics and may involve topical chemotherapeutics, curettage and electrodesiccation, surgical excision, electrocautery, or cryosurgery.

Prevention of Squamous Cell Carcinoma in Situ

Because many skin cancers seem to be related to ultraviolet (UV) exposure, a number of measures are recommended to limit exposure.

  • Sun avoidance: Seeking shade, minimizing outdoor activities between 10 AM and 4 PM (when sun's rays are strongest), and avoiding sunbathing and the use of tanning beds

  • Use of protective clothing: Long-sleeved shirts, pants, and broad-brimmed hats

  • Use of sunscreen: At least sun protection factor (SPF) 30 with broad-spectrum UVA/UVB protection, used as directed (ie, reapplied every 2 hours and after swimming or sweating); should not be used to prolong sun exposure

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