A 59-year-old woman presents for evaluation of a growth on her left forearm that has been present for approximately 3 months. The lesion has been increasing in size and is occasionally tender to touch. She is a cigarette smoker and admits to ample past sun and indoor ultraviolet light exposure. Her medical history includes a basal cell carcinoma that was surgically removed from her back 2 years previously. Her skin appears aged in general, with hyperpigmentation and loss of elastic tissue. The lesion in question has an erythematous base and a hyperkeratotic center.
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A biopsy was performed showing the lesion to be hypertrophic actinic keratosis. Actinic keratoses are areas of atypical squamous transformation that arise secondary to chronic ultraviolet light exposure. They are of importance clinically because a small percentage can evolve into squamous cell carcinoma.1 Actinic keratoses occur most commonly on the face, scalp, and extremities. Several histologic types of actinic keratoses have been described, including atrophic, bowenoid, acantholytic, pigmented, lichenoid, and hypertrophic.2 Hypertrophic actinic keratoses may resemble lesions of lichen simplex chronicus as a result of intermittent trauma and rubbing.3
In a study that included 50 hyperkeratotic papules of the hands, 10% proved to be of the hypertrophic variety.4 Of those, a significant percentage was either associated with or evolving into squamous cell carcinoma. This is important to recognize because many topical therapies are approved by the US Food and Drug Administration to treat actinic keratosis but are generally reserved for the non-hypertrophic variety. These include 5-fluorouracil, imiquimod, ingenol mebutate, and diclofenac sodium.5 The best treatment for the lesion in the patient described in this case would be surgical removal.
Stephen Schleicher, MD, is an associate professor of medicine at the Commonwealth Medical College in Scranton, Pennsylvania, and an adjunct assistant professor of dermatology at the Perelman School of Medicine at the University of Pennsylvania in Philadelphia. He practices dermatology in Hazleton, Pennsylvania.
- Ratushny V, Gober MD, Hick R, Ridky TW, Seykora JT. From keratinocyte to cancer: the pathogenesis and modeling of cutaneous squamous cell carcinoma. J Clin Invest. 2012;122:464-472.
- Weedon D. Actinic keratosis. In: Weedon D. Weedon’s Skin Pathology. 3rd ed. London, UK: Churchill Livingstone/Elsevier; 2010:676-679.
- Billano RA, Little WP. Hypertrophic actinic keratosis. J Am Acad Dermatol. 1982;7:484-489.
- Suchniak JM, Baer S, Goldberg JH. High rate of malignant transformation in hyperkeratotic actinic keratoses. J Am Acad Dermatol. 1997;37:392-394.
- Stockfleth E. The paradigm shift in treating actinic keratosis: a comprehensive strategy. J Drugs Dermatol. 2012;11:1462-1467.