What is Solar Keratoses: Precancerous Spots?
Solar keratoses, also known asactinic keratoses, are dry, scaly rough spots, patches or bumps that form on the outermost layer of the skin and range in color from fleshy pink to reddish-brown. Occasionally they can grow upwards, resembling a “horn” (cutaneous horn). These lesions occur after years of exposure to ultraviolet light and represent significantly sun-damaged skin. They are commonly found over the face, ears, neck, lower arms and the back of the hands; and may sometimes even occur on the lower lip as persistently scaly cracked spots.
Solar keratosis is considered the earliest stage in the development of skin cancer and is therefore known as a “precancer”. Although the vast majority of solar keratoses remain benign, studies have reported that up to 10% may progress to squamous cell carcinoma – a type of skin cancer that can spread within the body and be life-threatening.
What Causes Solar Keratosis?
Solar keratoses occur when the cells of the top layer of skin (the epidermis) are damaged through ultraviolet radiation, typically from sunlight, commercial tanning lamps and beds. You may be more likely to develop solar keratoses if you have the following risk factors:
- Fair skin, red or blond hair and blue or light-colored eyes
- A tendency to freckle or burn easily when exposed to sunlight
- A personal history of actinic keratosis or skin cancer
- A history of frequent or intense sun exposure or sunburn
- A weak immune system as a result of chemotherapy, chronic leukemia, AIDS or organ transplant medications
How is Solar Keratosis Treated?
A variety of strategies are available for the treatment of solar keratosis:
- Cryotherapy is one of the most common treatments and involves applying liquid nitrogen by spray or other applicator to freeze the solar keratoses off. It is a simple and effective procedure that does not require anesthesia and produces no bleeding.
- Curettage & Cautery is another treatment that involves scraping the lesion off followed by cautery to control the bleeding.
- A Shave or Excisional Biopsy may also be carried out to obtain a specimen for testing for squamous cell carcinoma or other skin cancer.
- 5-fluorouracil Cream (5-FU) is most useful when there are many solar keratoses on the face. The cream generally needs to be applied on the skin once or twice a day for two to four weeks. The treated areas become red and raw, and can be quite uncomfortable. Healing starts when the cream is discontinued.
- Imiqimod Cream is a cream-based immune response modifier and can be applied to areas affected by solar keratoses two or three times per week for between four and 16 weeks. Like 5-FU, it also causes an inflammatory reaction that is maximal at about three weeks and generally settles down with continued use.
- Photodynamic Therapy (PDT) involves applying a photosensitizer chemical to the affected area prior to exposing it to a strong source of visible light or laser. The treated area develops a “burn” effect then heals over a couple of weeks.
Prevention and Early Detection
Sun safety is necessary to prevent the development and recurrence of solar keratosis and other skin cancers. Avoiding deliberate tanning from the sun and tanning beds is essential. Apply sunscreen to all exposed skin before going outdoors. Choose a broad spectrum sunscreen that protects against both UVA and UVB rays and has a Sun Protection Factor (SPF) of at least 30. Reapply sunscreen approximately every two hours – even on cloudy days. Covering up with long sleeves, pants, wide brimmed hats and sunglasses also help to protect against UVA and UVB rays.