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INTRODUCTION TO CHAPTER

Actinic keratoses (AKs) are one of the most common skin findings in dermatology. An AK is a neoplasm of the epidermis and considered as a precursor lesions to squamous cell carcinoma (SCC). Ultraviolet (UV) light exposure is the main cause of AKs. They are very common in sun-exposed skin, especially in the light skin type and, elderly patients. The presence of several AKs may be an indicator that the patient has incurred sufficient sun damage for increased risk of basal cell carcinoma and squamous cell carcinoma.

Basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) are the most common types of skin cancers and the most common of all cancers in the United States.3 Both are caused by UV light exposure and usually occur on sun-exposed skin. BCCs and SCCs are sometimes called "non-melanoma skin cancer (NMSC)" and are readily treatable if detected early. BCCs are the most common type of skin cancer in the immunocompetent individual and rarely metastasize. SCCs are the second most common skin cancer in the immunocompetent individual and can metastasize to regional lymph nodes if not treated early. Routine skin examinations are crucial to early detection. Sun avoidance and protection with proper habits, clothing, and sunscreen are important for the prevention of BCCs and SCCs.4

ACTINIC KERATOSIS

Introduction

Actinic keratoses are precancerous lesions of the keratinocytes and are very common in individuals over the age of 55 years with light skin types. They mostly develop in sun-exposed areas of the skin such as the head, neck, and distal extremities. Damage caused by UV light exposure is the predominant cause. Lighter skin type and genetic predisposition makes some patients especially susceptible. If untreated, a small percentage of AKs will transform into SCC. Appropriate treatment during the precancerous phase is less invasive and aimed at preventing transformation.1

Pathogenesis

AKs develop after intense or long-term exposure to UV light (natural or artificial). Chronic sun exposure may lead to p53 tumor suppressor gene mutation of individual keratinocytes in the epidermis.2 The same genetic mutations are seen in AKs and SCCs. The mutations will lead to propagation of the abnormal keratinocytes leading to faster division of these cells and development of a clinically apparent lesion. If left untreated, approximately 10% of AKs may become SCCs.

Clinical Presentation

History

Patients typically complain of persistent scaly rough lesions (several at once is common) on frequently sun-exposed areas such as the face, scalp, and ears. Dorsal hands and forearms in men and lower legs in women are also commonly affected areas. The lesions usually do not have any symptoms such as itching or pain. Patients often scratch off the overlying scale, only to have it recur.

Physical ...

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