With time, actinic keratoses may develop into invasive cutaneous horns or skin cancers. Development of actinic keratoses may occur in patients as early as their 20s and 30s, who live in areas of high solar radiation, are fair-skinned, and do not use sunscreen for photoprotection. Usually patients demonstrate a background of solar damaged skin with telangiectasias, elastosis, and pigmented lentigines. Histologically, the epidermal changes are characterized by acanthosis, parakeratosis, and dyskeratoses. Cellular atypia is present and the keratinocytes vary in size and shape.
Mitotic figures are common.
This presentation may resemble Bowen Disease or carcinoma in situ. Often, marked hyperkeratosis and areas of parakeratosis with loss of the granular layer are present. A dense inflammatory infiltrate usually is present. Quite often the invasive carcinomas that develop from these actinic keratoses are the less aggressive type and the prognosis usually is excellent. Distant metastases are extremely rare.