Chapter 17: Actinic Keratosis, Basal, and Squamous Cell Carcinoma

INTRODUCTION TO CHAPTER

Actinic keratoses (AKs) are one of the most common skin findings in dermatology. AKs are benign neoplasms of the epidermis and are considered precursor lesions to nonmelanoma skin cancers. They are very common in sun-exposed areas of the skin, especially in the elderly patient. Ultraviolet light exposure is the main cause of AKs.

Basal cell carcinomas (BCCs) and squamous cell carcinomas (SCCs) are the most common types of skin cancers and the most common cancers in the United States.¹ Both are commonly seen in sun-exposed areas of the skin and are readily treatable if detected early. BCCs are the most common type of skin cancer and rarely metastasize. SCCs are the second most common skin cancer and can metastasize to regional lymph nodes if not treated early. Sun avoidance, use of proper clothing and sun screens, and routine examinations are important for prevention of nonmelanoma skin cancers.

ACTINIC KERATOSIS

Introduction

Actinic keratoses (AKs) are precancerous lesions of the keratinocytes and are very common in the elderly Caucasian population. They typically occur on sun-exposed areas such as the head and neck areas, as well as the distal extremities. Ultraviolet (UV) light exposure is the most common cause of AKs, with a genetic predisposition also being important. An AK is a precursor lesion to SCC and should be treated with appropriate therapy.²

Pathophysiology

Actinic keratoses 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 visible lesion. If left untreated, approximately 10% of actinic keratosis may become SCCs.

Clinical Presentation

History

Patients typically complain of a scaly rough lesion(s) 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 try to scratch off the overlying crust, only to have the scaly surface reform.

Physical Examination

Actinic keratoses can present as a solitary lesion or as a larger, diffuse plaque. Solitary lesions often appear as an ill-defined, scaly, rough, red plaque that is approximately 3 to 6 mm in diameter. The lesions can be slightly sensitive to touch. Solitary AKs can also present as a more keratotic papule with a thicker stratum corneum above the base of the lesion (Figure 17-1). This type of a lesion can resemble a cutaneous horn and is frequently referred to ...