Topical management of actinic keratosis and field cancerisation.

Actinic keratosis (AK) is a squamous cell carcinoma of the epidermis in situ. In around 10% of all patients with AK and in approximately 30% of patients with additional immune suppression an invasive squamous cell carcinoma of the skin is subsequently observed highlighting that AKs should be identified and treated early. The hallmarks and characteristic features of non-melanoma skin cancer have been defined histologically: histopathology allows the differentiation based on a small tissue sample and remains the gold standard for diagnosis. For all therapies the objective is to cure lesions, both clinically and histologically, by the destruction of mutated keratinocytes and to reduce the numbers of AK lesions with the minimum of pain, scarring and recurrence. The presence of AKs are related to exposure to ultra violet radiation, thus all treatments should be combined with a reduction in exposure to sunlight. There are a number of treatment options currently available, including excision, curettage and desiccation, cryotherapy, laser therapy or topical treatments including, imiquimod, photodynamic therapy, cox-1/2 inhibitors, chemical peels or 5-fluorouracil, but not all are appropriate for all patients or all lesions. Often treatments are individualized to ensure maximum response. Although existing treatments can be highly effective, they have certain limitations such as poor patient tolerability or, particularly as AKs occur on exposed areas, they are cosmetically unacceptable. In addition, recurrence rates vary for different treatments. Recurrence of a lesion (which by definition affects the same site) is often the result of incomplete removal of clinically apparent AK lesions after treatment or the presence of subclinical lesions that were not identified and removed. AK lesions can be treated individually or, if the lesions are numerous in an area of sun-damaged skin the whole area should be treated to remove subclinical lesions as well as those clinically visible (field-directed therapy).Overall the treatment choice is based on several factors, including location and number of lesions, growth and morphology, area of sun-damaged skin, age, lifestyle, and factors related to previous treatment or patient history.