Core Dermatology Diagnoses / CategoriesNeoplastic Benign and Malignant

Actinic keratosis

Author: Faculty Reviewers:

Publish date: Posted on
Last updated: September 6, 2023

Keywords #

sun damage
skin cancer
actinic
keratosis

Diagnosis #

Actinic keratoses (AK) are considered premalignant skin lesions that present as erythematous, gritty macules, papules, or plaques; however, not all AKs evolve into skin cancer. AKs commonly present on sun-exposed areas of the body as their pathogenesis is related to ultraviolet (UV) radiation. UV radiation induces a mutation in p53, a known tumor suppressor gene, which allows cells with DNA damage to grow clonally.[1] Studies have shown that a single sunburn can increase the risk of AKs.[2]

AKs have the potential to progress into squamous cell carcinoma and are thus routinely treated. While the rate of transformation is low – 0.075–0.096% per lesion per year, about 60% of cutaneous squamous cell carcinomas arise from a preexisting AK.[3,4]

Key Concepts #
  • Actinic keratoses (AK) present as gritty, erythematous macules, papules, or plaques on sun-exposed skin.
  • Ultraviolet exposure increases the risk of developing AKs.
  • AKs have the potential to become squamous cell carcinoma.
  • There are multiple treatments for limited and wide-spread disease.
Epidemiology #

AKs more commonly affect individuals with fair skin. Older age is also a risk factor given the higher cumulative dose of sun exposure. In those with relatively high sun exposure, AKs are present in 55% of Caucasian men and 37% of Caucasian women between the ages of 65 – 74 years. African Americans do not commonly develop AKs.[4] Genetic disorders (i.e. xeroderma pigmentosum), infections (i.e. HPV), and immunosuppression are also risk factors for developing AKs.[5,7]

Clinical Features #
  • AKs are most common on the scalp, face, dorsal forearms and hands.
  • They can often be felt before they are seen with a texture akin to sand paper.
  • An erythematous base is usually present.
  • There are many clinical variants including classic, atrophic, hypertrophic, or pigmented.
  • Some AKs have a keratotic projection that is cone-shaped known as a cutaneous horn.
Differential Diagnoses #
  • Squamous cell carcinoma
  • Inflamed seborrheic keratosis
  • Seborrheic dermatitis
  • Psoriasis
  • Bowen’s disease
  • Squamous cell carcinoma in situ
  • Verrucous keratosis
  • Porokeratosis
  • Common wart
Diagnostic Workup #

AKs are usually diagnosed clinically; however, if the lesion is large (>1 cm), indurated, or tender, a biopsy is warranted to confirm diagnosis. Biopsy threshold should be lower for patients who are immunosuppressed, or in whom the lesion has previously been treated. Histopathology reveals atypical keratinocytes with pleomorphic and hyperchromatic nuclei. The ‘flag sign’ is common in hypertrophic AKs and refers to alternating areas of ortho- and parakeratosis.

Treatment #

Patients who present with few, isolated, discrete lesions are generally treated with cryotherapy or curettage.  Field therapy with topical 5-fluorouracil (most effective) or photodynamic therapy is more effective for patients with numerous diffuse AKs over a large surface area.

The best treatment is prevention of lesions with aggressive sun protection. This includes broad-brimmed hats, long sleeves, and sunscreen with at least SPF 30.

Slide Viewer #
https://utahderm.med.utah.edu/image-viewer/?diagnosis=actinic_keratosis
References #
  1. Leffell DJ. The scientific basis of skin cancer. J Am Acad Dermatol 2000; 42:18. 
  2.  Frost CA, Green AC, Williams GM. The prevalence and determinants of solar keratoses at a subtropical latitude (Queensland, Australia). Br J Dermatol 1998; 139:1033. 
  3.  Marks R, Rennie G, Selwood TS. Malignant transformation of solar keratoses to squamous cell carcinoma. Lancet 1988; 1:795. 
  4.  Criscione VD, Weinstock MA, Naylor MF, et al. Actinic keratoses: Natural history and risk of malignant transformation in the Veterans Affairs Topical Tretinoin Chemoprevention Trial. Cancer 2009; 115:2523. 
  5. Engel A, Johnson ML, Haynes SG. Health effects of sunlight exposure in the United States. Results from the first National Health and Nutrition Examination Survey, 1971-1974. Arch Dermatol 1988; 124:72. 
  6. McBride P, Neale R, Pandeya N, Green A. Sun-related factors, betapapillomavirus, and actinic keratoses: a prospective study. Arch Dermatol 2007; 143:862. 
  7. Keller B, Braathen LR, Marti HP, Hunger RE. Skin cancers in renal transplant recipients: a description of the renal transplant cohort in Bern. Swiss Med Wkly 2010; 140:w13036. 
Contents