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Key Clinical Updates in Miscellaneous Scaling Dermatoses

Fluorouracil cream is the most effective topical agent for field treatment of actinic keratosis. Imiquimod, ingenol mebutate, and photodynamic therapy are also effective.

Isolated scaly patches may represent actinic (solar) keratoses, nonpigmented seborrheic keratoses, or Bowen or Paget disease.


Actinic keratoses are small (0.2–0.6 cm) macules or papules—flesh-colored, pink, or slightly hyperpigmented—that feel like sandpaper and are tender to palpation. They occur on sun-exposed parts of the body in persons of fair complexion. Actinic keratoses are considered premalignant, but only 1:1000 lesions per year progress to become squamous cell carcinomas.

Application of liquid nitrogen is a rapid method of eradication. The lesions crust and disappear in 10–14 days. “Field treatment” (treatment over an area, rather than targeted treatment to one lesion) with a topical agent to the anatomic area where the actinic keratoses are most prevalent (eg, forehead, dorsal hands, etc) can be considered in patients with multiple lesions in one region. Fluorouracil cream is the most effective topical agent used for field treatment; imiquimod and ingenol mebutate are also effective, as is photodynamic therapy. Any lesions that persist should be evaluated for possible biopsy.

Arenberger  P  et al. New and current preventive treatment options in actinic keratosis. J Eur Acad Dermatol Venereol. 2017 Sep;31(Suppl 5):13–7.
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Jansen  MHE  et al. Randomized trial of four treatment approaches for actinic keratosis. N Engl J Med. 2019 Mar 7;380(10):935–46.
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Siegel  JA  et al. Current perspective on actinic keratosis: a review. Br J Dermatol. 2017 Aug;177(2):350–8.
[PubMed: 27500794]


Bowen disease (intraepidermal squamous cell carcinoma) can develop on both sun-exposed and non–sun-exposed skin. The lesion is usually a small (0.5–3 cm), well-demarcated, slightly raised, pink to red, scaly plaque and may resemble psoriasis or a large actinic keratosis (eFigure 6–43). These lesions may progress to invasive squamous cell carcinoma. Excision or other definitive treatment such as topical treatment (fluorouracil or imiquimod) or photodynamic therapy is indicated.

eFigure 6–43.

This isolated, scaly patch on a patient's arm turned out to be Bowen disease (intraepidermal squamous cell carcinoma) on biopsy. (Used, with permission, from S Goldstein, MD.)

Extramammary Paget disease, a manifestation of intraepidermal carcinoma or underlying genitourinary or gastrointestinal cancer, resembles chronic eczema and usually involves apocrine areas such as the genitalia. Mammary Paget disease of the nipple, a unilateral or rarely bilateral red scaling plaque that may ooze, is associated with an underlying intraductal mammary carcinoma (Figure 17–4). While these lesions appear as red patches and plaques in fair-skinned persons, in darker-skinned individuals, hyperpigmentation may be prominent.

Edey  KA  et al. Interventions for ...

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