These growths are more common in fair-skinned people and those who are frequently in the sun.[7] They are believed to form when skin gets damaged by UV radiation from the sun or indoor tanning beds, usually over the course of decades. Given their pre-cancerous nature, if left untreated, they may turn into a type of skin cancer called squamous cell carcinoma.[5] Untreated lesions have up to a 20% risk of progression to squamous cell carcinoma,[8] so treatment by a dermatologist is recommended.
Actinic keratoses characteristically appear as thick, scaly, or crusty areas that often feel dry or rough. Size commonly ranges between 2 and 6 millimeters, but they can grow to be several centimeters in diameter. AKs are often felt before they are seen, and the texture is sometimes compared to sandpaper.[9] They may be dark, light, tan, pink, red, a combination of all these, or have the same color as the surrounding skin.
Given the causal relationship between sun exposure and AK growth, they often appear on a background of sun-damaged skin and in areas that are commonly sun-exposed, such as the face, ears, neck, scalp, chest, backs of hands, forearms, or lips. Because sun exposure is rarely limited to a small area, most people who have an AK have more than one.[10]
If clinical examination findings are not typical of AK and the possibility of in situ or invasive squamous cell carcinoma (SCC) cannot be excluded based on clinical examination alone, a biopsy or excision can be considered for definitive diagnosis by histologic examination of the lesional tissue.[11] Multiple treatment options for AK are available. Photodynamic therapy (PDT) is one option for the treatment of numerous AK lesions in a region of the skin, termed field cancerization.[12] It involves the application of a photosensitizer to the skin followed by illumination with a strong light source. Topical creams, such as 5-fluorouracil or imiquimod, may require daily application to affected skin areas over a typical time course of weeks.[13]
Cryotherapy is frequently used for few and well-defined lesions,[14] but undesired skin lightening, or hypopigmentation, may occur at the treatment site.[15] By following up with a dermatologist, AKs can be treated before they progress to skin cancer. If cancer does develop from an AK lesion, it can be caught early with close monitoring, at a time when treatment is likely to have a high cure rate.
^Rapini RP, Bolognia J, Jorizzo JL (2007). Dermatology: 2-Volume Set. St. Louis: Mosby. pp. Chapter 108. ISBN978-1-4160-2999-1.
^Logan CM, Rice MK (1987). Logan's Medical and Scientific Abbreviations. J. B. Lippincott and Company. p. 512. ISBN0-397-54589-4.
^Moy RL (January 2000). "Clinical presentation of actinic keratoses and squamous cell carcinoma". Journal of the American Academy of Dermatology. 42 (1 Pt 2): 8–10. doi:10.1067/mjd.2000.103343. PMID10607350.
^Stockfleth E, Kerl H (Nov–Dec 2006). "Guidelines for the management of actinic keratoses". European Journal of Dermatology. 16 (6): 599–606. PMID17229598.
^Werner RN, Stockfleth E, Connolly SM, Correia O, Erdmann R, Foley P, Gupta AK, Jacobs A, Kerl H, Lim HW, Martin G, Paquet M, Pariser DM, Rosumeck S, Röwert-Huber HJ, Sahota A, Sangueza OP, Shumack S, Sporbeck B, Swanson NA, Torezan L, Nast A (November 2015). "Evidence- and consensus-based (S3) Guidelines for the Treatment of Actinic Keratosis - International League of Dermatological Societies in cooperation with the European Dermatology Forum - Short version". Journal of the European Academy of Dermatology and Venereology. 29 (11): 2069–79. doi:10.1111/jdv.13180. PMID26370093. S2CID19644716.
^Szeimies RM, Torezan L, Niwa A, Valente N, Unger P, Kohl E, Schreml S, Babilas P, Karrer S, Festa-Neto C (July 2012). "Clinical, histopathological and immunohistochemical assessment of human skin field cancerization before and after photodynamic therapy". The British Journal of Dermatology. 167 (1): 150–9. doi:10.1111/j.1365-2133.2012.10887.x. PMID22329784. S2CID10970924.
^Thai KE, Fergin P, Freeman M, Vinciullo C, Francis D, Spelman L, Murrell D, Anderson C, Weightman W, Reid C, Watson A, Foley P (September 2004). "A prospective study of the use of cryosurgery for the treatment of actinic keratoses". International Journal of Dermatology. 43 (9): 687–92. doi:10.1111/j.1365-4632.2004.02056.x. PMID15357755. S2CID24067576.