INTRODUCTION
Actinic Keratosis and Field Cancerization Concepts
Actinic keratosis (AK) is clinically characterized as rough, scaly patches or spots on the skin with a variable degree of hyperkeratosis. AK is a chronic disease that usually affects skin areas that are long-term exposed to ultraviolet (UV) radiation from the sun,1 such as the face or scalp. Its prevalence is high and is likely to rise in the coming years,2,3 with an increasing incidence in the aging population.4
Histologically, AK demonstrates atypia of the basal layer of the epidermis, often associated with parakeratosis,5 and usually coexists with surrounding non-visible lesions. However, the whole area is prone to the development of invasive skin cancers, a process known as 'field cancerization'.
Field cancerization has significant clinical consequences and therapeutic implications for AK, including the advantages of exploiting field treatments compared with lesion-directed ones. Moreover, this aspect deserves special attention because it implies that AK lesions should not be characterized by discrete stages.
The categorization of individual AK lesions often fails in its attempt to define unambiguous boundaries between their different evolutionary stages, such as the 3-stage Olsen's classification. This problem could be avoided by adopting a continuous dimensional approach that incorporates and analyzes more aspects of the disease (ie, lesion count, overall sun-damaged area, characteristics of all lesions globally in the context of the affected region), beyond individual lesion assessment. The same region may present AK lesions in different stages or even progressive AK. Three-dimensional staging leads to the problem that these stages can be misinterpreted as progression steps from grade I (mild) to grade III (severe). However, this is not the case when talking about hyperkeratosis - these are simply different grades of classification, descriptive stages, that should be not misjudged in terms of progression. Long-term sun exposure of the skin gives the diagnosis of AK a progressive and chronic character6 that should be reflected in its categorization.
Moreover, an algorithm has been proposed that complements existing evidence-based guidelines to differentiate patients
Actinic keratosis (AK) is clinically characterized as rough, scaly patches or spots on the skin with a variable degree of hyperkeratosis. AK is a chronic disease that usually affects skin areas that are long-term exposed to ultraviolet (UV) radiation from the sun,1 such as the face or scalp. Its prevalence is high and is likely to rise in the coming years,2,3 with an increasing incidence in the aging population.4
Histologically, AK demonstrates atypia of the basal layer of the epidermis, often associated with parakeratosis,5 and usually coexists with surrounding non-visible lesions. However, the whole area is prone to the development of invasive skin cancers, a process known as 'field cancerization'.
Field cancerization has significant clinical consequences and therapeutic implications for AK, including the advantages of exploiting field treatments compared with lesion-directed ones. Moreover, this aspect deserves special attention because it implies that AK lesions should not be characterized by discrete stages.
The categorization of individual AK lesions often fails in its attempt to define unambiguous boundaries between their different evolutionary stages, such as the 3-stage Olsen's classification. This problem could be avoided by adopting a continuous dimensional approach that incorporates and analyzes more aspects of the disease (ie, lesion count, overall sun-damaged area, characteristics of all lesions globally in the context of the affected region), beyond individual lesion assessment. The same region may present AK lesions in different stages or even progressive AK. Three-dimensional staging leads to the problem that these stages can be misinterpreted as progression steps from grade I (mild) to grade III (severe). However, this is not the case when talking about hyperkeratosis - these are simply different grades of classification, descriptive stages, that should be not misjudged in terms of progression. Long-term sun exposure of the skin gives the diagnosis of AK a progressive and chronic character6 that should be reflected in its categorization.
Moreover, an algorithm has been proposed that complements existing evidence-based guidelines to differentiate patients
