A new vision of actinic keratosis beyond visible clinical lesions

Abstract

In actinic keratosis (AK), clinical and subclinical lesions coexist across large areas of sun-exposed skin resulting in field cancerization. The lesions are part of a disease continuum which can progress into invasive squamous cell carcinoma (SCC). Conventional biopsy sampling together with histopathological analysis of the excised tissue is still the gold standard for differentially diagnosing AK from invasive SCC and identifying the characteristic pathophysiological features of these lesions. Given that biopsy sampling is invasive and not suited to the investigation of disease across large fields of skin, several imaging technologies have been applied to non-invasively investigate AK. Widely available imaging technologies such as cross-polarized light, fluorescence and dermoscopy can assist the dermatologist in diagnosing AK and in identifying different types of AK lesions. Modern imaging technologies such as reflectance confocal microscopy (RCM) and high-definition optical coherence tomography (HD-OCT) provide high-resolution images of the skin. These techniques can be used to image the histological changes that characterize AK and so can be used to diagnose the disease and its severity. They can also identify the presence of subclinical lesions and non-invasively monitor the effects of AK treatments on both subclinical and clinical lesions over time. Both RCM and HD-OCT have revealed a new vision of AK by visualizing in detail the cellular and histological changes that characterize both clinical and subclinical lesions, and confirming that the disease affects the entire sun-exposed field. As a consequence of these findings, the target for the treatment of AK now needs to be the detection and clearance of all clinical and subclinical lesions across the entire sun-exposed field.

Real-world approach to actinic keratosis management: practical treatment algorithm for office-based dermatology

“…In the future, novel imaging techniques such as reflectance confocal microscopy and optical coherence tomography may be useful in the diagnosis of AK (5,26,27).…”

“…Treatment success parameters should ideally also take into consideration the ability of a therapy to eliminate subclinical lesions, though this depends on these lesions becoming detectable during treatment, or the use of specific imaging techniques for field cancerization (which are not usually available in dermatological offices) (26).…”

How Wounding via Lasers Has Potential Photocarcinogenic Preventative Effects via Dermal Remodeling

“…Prevention of tumors before they become clinically manifested has always been the most affordable though not necessarily the most elusive way. SCC is considered to evolve from pre-cancerous entity - the actinic keratosis (AK) (31), a lesion previously been shown to be somewhat manageable by cryotherapy, curettage, electrosurgery and photodynamic therapy with 5-fluorouracil or topical imiquimod (32,33). It has been shown that if treat AK by these modalities early enough that the progression to SCC is highly unlikely.…”

Ingenol Mebutate 0.06% Gel for Field Treatment of Actinic Keratosis on 250 cm2 of Skin on Trunk and Extremities: A Randomized Dose-Finding Trial

“…3,5,6 Advanced imaging techniques show that areas of sun-exposed skin may contain both sub-clinical and clinically visible lesions, as well as areas of dysplastic cells in fields of cancerization. [6][7][8] Treating the entire field of sun-damaged skin, rather than only the clinically apparent lesions, is therefore ideal. Ingenol mebutate (IngMeb) (Picato ® LEO Pharma A/S Ballerup, Denmark) is indicated for the topical treatment of AK in areas of skin up to 25 cm 2 .…”