What is Solar Keratosis?
Solar Keratosis are known as Sunspots. These rough scaly lesions on the backs of hands & forearms, face & forehead are very common in Australia!
How do sun spots form?
The p53 gene codes a protein that suppresses abnormal growth of cells. UVB damages this tumor suppressor gene so that abnormal cells start to appear, manifesting as inflamed, scaley skin called ‘sun spots.’
Do Sunspots matter?
Sunspots can be thought of as the skin-equivalent of being overweight in that Sunspots:
- occur in most older Australians.
- Are more common with age
- Reflect a combination of environment and genes.
- Are a risk factor rather than a major problem in their own right.
- Early treatment leads to the best outcome.
Solar keratosis is almost to be expected if you were brought up in Australia, have fair skin, and are over the age of 40 to 45. In fact, Sunspots affect around 80% of people by the age of 60¹.
Why do sunspots matter if so of us get them?
- The presence of Solar Keratosis indicates significant exposure to past ultraviolet light radiation and a higher risk of skin cancer in general.
- Solar Keratosis may develop into an important type of skin cancer: SCC (Squamous Cell Carcinoma). Indeed, Solar Keratosis is the mild end of a continuous spectrum – from Solar keratosis to IEC (Intraepidermal Carcinoma) to SCC.
- A lesion may look like Solar Keratosis but be a skin cancer. Pigmented Solar Keratosis may appear similar to Melanoma whilst thicker Solar Keratosis can look very similar to IEC.
Because of the risk of transition of Solar Keratosis to Squamous cell carcinoma, areas of solar keratosis are therefore generally treated. The precise risk of a specific untreated Solar Keratosis developing into SCC is not known for certain. One figure from a study suggests that there is a 10% chance that a person with 7 to 8 untreated Solar Keratoses will go onto to develop one SCC within 10 years. Research suggests that 60 to 80% of SCC arises from solar keratosis.
Some Solar Keratoses may go away on their own without any treatment other than good regular sun protection.
What does a Sunspot look like?
The typical solar keratosis will be a red flat scaly area on the back of the hands, forearms, face or scalp (in men with hair loss). They are often better felt than seen. A sunspot is usually less than 1cm in diameter although sunspots may be grouped together as an almost continuous area of ‘field change’ that reflects an area of UV-damaged skin.
The appearances can vary hugely. There are different subtypes depending on their clinical appearance:
Classic Solar Keratosis (as described above – flat, scaly and red). Need to differentiate from an IEC.
Hypertrophic Solar Keratosis – These are raised from the skin (sometimes markedly raised) and covered with a thick scale on a red base. These can look similar to SCC.
Cutaneous horn – These are thin hard lesions that project up from the skin and are quite firm and often dark. Hence the term ‘horn’ which may also be caused by SCC or a viral wart.
Pigmented Solar Keratosis: found most commonly on the face and can look like a melanoma.
Actinic Cheilitis: Solar Keratosis on the lips. More common on the lower lips.
A dermatoscope may be needed to examine the lesion closely to help confirm that the lesion is a Solar Keratosis and not a skin cancer or alternative diagnosis. When there is doubt then a biopsy will be required.
Treatment Comparison Table
|Effectiveness||Treatment Schedule||Side Effects Severity||Duration of Side Effects||Cosmetic Outcome||Price||Treatment Area|
|Efudix (5FU)||Moderately effective||2-4 weeks of twice daily application||Marked||1-2 weeks after stopping treatment||Usually Good||$||Large areas|
|PDT (Photodynamic Therapy) – clinic||Effective||one or two visits||Moderate but can be painful||1-2 weeks||Good to Best||$$$$||Large areas|
|PDT (Photodynamic therapy) – daylight||Effective||one or two visits||Mild to Moderate||1-2 weeks||Good to Best||$$$||Particularly good for the face and scalp|
|Aldara||Moderately Effective||3x overnight applications per week for 4 weeks||Marked||1-2 weeks after stopping treatment||Usually Good||$$||Small – Maximum treatment area: 5cm by 5cm|
|Picato Gel||New to the Market – moderately effective compared to placebo||2 -3 days with once daily applications||Marked||7-10 days||Should be the same as Efudix or Aldara||$$$||Small – Maximum treatment area: 5cm by 5cm|
|Solaraze Gel||Generally Not considered very effective||3 months of twice daily applications||Minimal||Treatment Duration||Neutral||$||Small to Moderate|