Dermoscopy of Squamous Cell Carcinoma and Keratoacanthoma

Overview / Definition Squamous Cell Carcinoma (SCC) is a malignant tumor arising from keratinocytes in the epidermis. It is characterized by uncontrolled proliferation of squamous cells and can invade surrounding tissues and metastasize. Keratoacanthoma (KA) is a well-differentiated variant of SCC, often presenting as a rapidly growing, dome-shaped nodule with a central keratin-filled crater. Epidemiology SCC is one of the most common skin cancers, with an estimated incidence of 20 per 100,000 persons per year in the United States. Risk factors include: Chronic sun exposure Immunosuppression (e.g., organ transplant recipients) History of actinic keratosis Tanning bed use Older age and fair skin type Keratoacanthoma is less common but often seen in older adults and is more prevalent in sun-exposed areas of the skin. Pathophysiology / Mechanism The pathogenesis of SCC involves multiple factors, including genetic mutations (e.g., in the TP53 gene), UV radiation exposure, and chronic inflammation. KA is thought to arise from a benign process that may be triggered by sun exposure or HPV infection, leading to rapid growth and a distinct histological appearance. Clinical Presentation SCC typically presents as a red, scaly plaque or an ulcerated nodule, often with a crusted surface. In contrast, KA appears as: A firm, flesh-colored or pink nodule Rapid growth over weeks to months A central keratin plug or crater Both lesions commonly occur on sun-exposed areas such as the face, ears, and hands. Diagnosis / Workup Dermoscopy plays a crucial role in the evaluation of SCC and KA. Key dermoscopic features include: For SCC: Irregular vascular patterns Keratinization (white to yellow areas) Crusted surface with a brownish hue For KA: Central keratin plug Periphery with a well-defined border Yellowish to whitish areas of keratinization A biopsy is often necessary to confirm the diagnosis and assess the depth of invasion. Treatment / Management Management strategies for SCC and KA