{"entity":{"id":"actinic-keratosis","kind":"term","name":"Actinic keratosis (solar keratosis): sun damage, not cancer","aka":["actinic keratosis","actinic keratoses","solar keratosis","solar keratoses","AK","sun spots","sunspots","pre-cancerous skin patches","L57.0"],"tldr":"Rough, scaly patches on skin that has had a lot of sun, commonest on the scalp, face, ears, forearms and backs of hands. They are not cancer and are not counted as cancer anywhere in the UK, but they mark skin that has been damaged enough to be worth watching, and a small proportion go on to become squamous cell carcinoma.","summary":"An actinic keratosis is a patch of keratinocytes that have accumulated ultraviolet damage. Two coding systems agree about what it is not. In ICD-10 it is L57.0, inside the chapter on diseases of the skin and subcutaneous tissue, in the block for skin changes due to chronic exposure to nonionizing radiation; that is not a neoplasm code, and the neoplasm chapter, where skin cancer lives as C44 and carcinoma in situ of skin as D04, is a different chapter of the same book. In ICD-O, the morphology system registries use, it is 8070/0, where the final digit means benign, and the classification pointedly did not give it 8070/2, the code that exists and means squamous cell carcinoma in situ. Both the fourth and the fifth editions of the WHO skin classification file it under carcinoma precursors rather than under carcinomas. No UK cancer registry registers actinic keratoses as cancer. That is why they are a glossary entry here and not a cancer page, and it is worth being explicit about, because being told you have a pre-cancer is frightening out of proportion to what it means.\n\nHow often one becomes a cancer is a question the literature answers carefully rather than confidently. In the largest prospective study, 7,784 actinic keratoses on the faces and ears of 169 participants in a chemoprevention trial were followed, and the risk of one progressing to a primary squamous cell carcinoma, invasive or in situ, was 0.60 percent at 1 year and 2.57 percent at 4 years; 55 percent of the lesions had disappeared by the 1-year follow-up and 70 percent by 5 years (Criscione 2009). The classic Australian study of 21,905 solar keratoses put the risk of one transforming within a year at less than 1 in 1,000 (Marks 1988). A systematic review found published rates from 0 to 0.075 percent per lesion-year, up to 0.53 percent per lesion in people with a previous skin cancer, regression rates for single lesions of 15 to 63 percent after a year, and concluded that 'currently, no reliable estimates concerning the frequency of AK developing into invasive carcinoma can be given' (Werner 2013). The British guideline quotes both the under 1 in 1,000 per annum figure and a modelled probability of about 10 percent of developing a squamous cell carcinoma within ten years for a person with an average of 7.7 lesions (de Berker 2017).\n\nThe reason those two framings differ is the reason the lesions matter at all. Per lesion the risk is tiny; per person with many lesions it is not, and the same study that found a low per-lesion risk also found that about 65 percent of all the squamous cell carcinomas and 36 percent of the basal cell carcinomas diagnosed in the cohort arose where an actinic keratosis had previously been seen (Criscione 2009). So an individual patch is very unlikely to be the one, and the skin that grows them is where the cancer will come from.\n\nWhat they do mean is that the skin around them is damaged too. Actinic keratoses usually come in numbers rather than singly, and the useful way to think about them is as visible marks in a wider field of sun-damaged skin, the phenomenon called field cancerisation. That is why treatment is often aimed at an area rather than at a spot, and why having many of them raises the chance of a squamous cell carcinoma somewhere in that area rather than at any particular lesion. The European consensus that adopted the term keratinocyte cancer includes actinic keratosis in the group as a keratinocyte-derived precursor, which is an accurate description of where it sits: on the same biological road as squamous cell carcinoma, a long way from the end of it.\n\nWhere actinic keratosis sits relative to the two pages beside it is worth stating plainly. Actinic keratosis is dysplasia in sun-damaged skin and is not registered as cancer. Bowen's disease is squamous cell carcinoma in situ, a carcinoma confined to the epidermis, and has its own page here. Invasive cutaneous squamous cell carcinoma has broken through into the dermis. The three are a sequence in principle and not a timetable in practice: most actinic keratoses never become anything, and most Bowen's disease never becomes invasive.","asOf":"2026-09-25","wikipedia":"https://en.wikipedia.org/wiki/Actinic_keratosis","links":[{"label":"WHO ICD-10 (2019): C43 to C44 melanoma and other malignant neoplasms of skin; D04 carcinoma in situ of skin; L57.0 actinic keratosis, under skin changes due to chronic exposure to nonionizing radiation","url":"https://icd.who.int/browse10/2019/en"},{"label":"IARC and the International Association of Cancer Registries: ICD-O-3.2 morphology and behaviour codes (actinic keratosis 8070/0; Bowen disease 8081/2; keratoacanthoma a related term under 8071/3; micronodular basal cell carcinoma shares 8097/3 with nodular, and sclerosing or morphoeic shares 8092/3 with infiltrating)","url":"http://www.iacr.com.fr/index.php?option=com_content&view=category&layout=blog&id=100&Itemid=577"},{"label":"Philipp-Dormston et al., Acta Dermato-Venereologica 2024;104:adv40601: a European consensus on the consistent use of the term 'keratinocyte cancer'","url":"https://doi.org/10.2340/actadv.v104.40601"},{"label":"Cancer Research UK: types of non-melanoma skin cancer","url":"https://www.cancerresearchuk.org/about-cancer/skin-cancer/types"},{"label":"Cancer Research UK: squamous cell carcinoma of the skin","url":"https://www.cancerresearchuk.org/about-cancer/skin-cancer/types/squamous-cell-carcinoma"},{"label":"Criscione, Weinstock, Naylor et al., Cancer 2009;115(11):2523 to 2530: actinic keratoses, natural history and risk of malignant transformation in the Veterans Affairs topical tretinoin chemoprevention trial (7,784 lesions in 169 participants)","url":"https://doi.org/10.1002/cncr.24284"},{"label":"Werner, Sammain, Erdmann, Hartmann, Stockfleth and Nast, British Journal of Dermatology 2013;169(3):502 to 518: the natural history of actinic keratosis, a systematic review","url":"https://doi.org/10.1111/bjd.12420"},{"label":"de Berker, McGregor, Mohd Mustapa, Exton and Hughes, British Journal of Dermatology 2017;176(1):20 to 43: British Association of Dermatologists' guidelines for the care of patients with actinic keratosis 2017","url":"https://doi.org/10.1111/bjd.15107"},{"label":"WHO Classification of Tumours Editorial Board: Skin tumours, 5th edition, volume 12 (IARC, Lyon, 2025), ISBN 978-92-832-4535-3","url":"https://publications.iarc.who.int/Book-And-Report-Series/Who-Classification-Of-Tumours/Skin-Tumours-2025"},{"label":"Elder, Massi, Scolyer and Willemze (eds): WHO Classification of Skin Tumours, 4th edition, volume 11 (IARC, Lyon, 2018)","url":"https://publications.iarc.who.int/Book-And-Report-Series/Who-Classification-Of-Tumours/WHO-Classification-Of-Skin-Tumours-2018"}],"tags":[],"related":["field-cancerisation","dysplasia","carcinoma-in-situ","in-situ"],"cancers":["cutaneous-scc","bowens-disease","skin-cancer","basal-cell-carcinoma"],"sections":["diagnostics","prevention"],"technologies":[],"targets":[],"drugs":[],"companies":[],"institutions":[],"pathways":[],"terms":["keratinocyte-cancer","keratoacanthoma","keratinocyte-cancer-counting","cscc-subtype-and-grade"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":["Why a page was considered and not written. The corpus's rule is that a cancer record is a tumour entity (docs/CANCER-PAGES.md). Actinic keratosis fails it on the two clearest available tests: it is coded 8070/0, benign, in ICD-O, and L57.0, outside the neoplasm chapter, in ICD-10, and it is registered as cancer by no UK registry. The corpus does give pages to in-situ carcinomas that carry a /2 behaviour code and are registered, which is why Bowen's disease has one and this does not. The line is the behaviour code rather than anybody's judgement of severity, which is what makes it possible to apply the same line to the next case, and what made it survive the WHO fifth edition's rearrangement of this same group of lesions.","Where the boundary with Bowen's disease actually sits, under the microscope. The British guideline describes it precisely: the dysplasia in an actinic keratosis 'may be restricted to the basal layer or may extend to full-thickness atypia', and at the point where it is full thickness 'the lesion is known as SCC in situ (Bowen disease)' (de Berker 2017). So the difference between the thing on this page and the thing on the next one is how far up the epidermis the abnormal cells reach, which is a continuum being cut at a line, and part of why the argument about whether an actinic keratosis is already a cancer has run for decades.","The number of lesions is the thing that changes management, and it is not counted in any national statistic. Because actinic keratoses are not registered, there is no national figure for how many people have them, and the burden they place on dermatology and general practice is invisible in the cancer statistics in exactly the way the keratinocyte cancers themselves are only partly visible (see `keratinocyte-cancer-counting`)."],"category":"Pathology"},"route":"/terms/actinic-keratosis/","neighbours":{"pathway":[{"id":"field-cancerisation","kind":"pathway","name":"Field cancerisation","route":"/pathways/field-cancerisation/"}],"term":[{"id":"carcinoma-in-situ","kind":"term","name":"Carcinoma in situ (CIS)","route":"/terms/carcinoma-in-situ/"},{"id":"dysplasia","kind":"term","name":"Dysplasia (pre-cancerous change)","route":"/terms/dysplasia/"},{"id":"in-situ","kind":"term","name":"In situ","route":"/terms/in-situ/"},{"id":"inherited-skin-cancer-syndromes","kind":"term","name":"Inherited syndromes that cause skin cancer: Gorlin syndrome and xeroderma pigmentosum","route":"/terms/inherited-skin-cancer-syndromes/"},{"id":"keratinocyte-cancer","kind":"term","name":"Keratinocyte cancer (and why 'non-melanoma skin cancer' is being retired)","route":"/terms/keratinocyte-cancer/"},{"id":"keratoacanthoma","kind":"term","name":"Keratoacanthoma: the tumour that may be a squamous cell carcinoma","route":"/terms/keratoacanthoma/"},{"id":"cscc-subtype-and-grade","kind":"term","name":"The subtype and grade on a cutaneous squamous cell carcinoma report","route":"/terms/cscc-subtype-and-grade/"},{"id":"keratinocyte-cancer-counting","kind":"term","name":"Why nobody knows how many skin cancers there are: the counting rule behind every figure","route":"/terms/keratinocyte-cancer-counting/"}],"cancer":[{"id":"basal-cell-carcinoma","kind":"cancer","name":"Basal cell carcinoma","route":"/cancers/basal-cell-carcinoma/"},{"id":"bowens-disease","kind":"cancer","name":"Bowen's disease (squamous cell carcinoma in situ)","route":"/cancers/bowens-disease/"},{"id":"cutaneous-scc","kind":"cancer","name":"Cutaneous squamous cell carcinoma","route":"/cancers/cutaneous-scc/"},{"id":"skin-cancer","kind":"cancer","name":"Skin cancer (all types)","route":"/cancers/skin-cancer/"}],"section":[{"id":"diagnostics","kind":"section","name":"Diagnostics & Biomarkers","route":"/fronts/diagnostics/"},{"id":"prevention","kind":"section","name":"Prevention & Risk","route":"/fronts/prevention/"}]}}