Solar Keratosis.

Sunspots are uiquitous in Australians over the age of 40.

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.

What is the treatment for Solar Keratosis?

Treatment may be targeted to individual Sunspots, or to a whole ‘field’ such as the face, scalp, forearm and/or back of hands. Treatment of a whole field will reduce the risk of solar keratosis appearing in those adjacent areas in the future. When in doubt, it’s generally best to treat a whole field.

Have you seen someone walking around with a crusty red nose, cheeks, forehead and/or temples? Most likely they are having field treatment for Solar Keratosis.

There are over ten different treatment options available. To cut to the chase, the most widely used treatments are efudix and cryotherapy.

Physical treatments may be used to treat individual Solar Keratosis or whole field:

  • Efudix ® (5FU): Effective field treatment, significant side effects – redness and soreness of the skin for several weeks.
  • Photodynamic Therapy (PDT):  Effective, excellent cosmetic results, generally well tolerated, expensive. Treatment period shorter than with Efudix or Aldara.
  • Aldara® (Imiquimod) : Effective, similar side effects to efudix. Maximal treatment area 5cm by 5cm.
  • Picato gel ®:  short course, more expensive than efudix. Maximal treatment area 5cm by 5cm.
  • Solaraze gel ®: helps minor solar keratosis. Not as effective as other treatments although side effects are minimal.

There are other topical therapies for mild solar keratosis

  • Salicyclic Acid 5% in sorbolene. Useful for reducing Scale prior to treatment. This may be bought direct from a pharmacy without prescription.
  • Retinoid Creams such as ®Adapalene and Tretinoin, though not approved by The TGA, may be helpful.

Regular use of a moisturizer is helpful.

Surgical treatments may be used to treat more isolated lesions:

  • Cryotherapy: Clearance of around 75%. Freeze time varies from 5 seconds for the thinnest lesions to 20 seconds for longer for thick lesions.
  • Formal Excision: When a biopsy is required to exclude, for example, squamous cell carcinoma. Stitches are required.
  • Curettage: The lesion is scraped off and heals without stitches.
  • Shave Excision: Similar to Curettage and heals without stitches.

Many regular attendees of a skin cancer clinic are familiar with Cryotherapy (freezing). The issue with cyotherapy is that it does not treat a whole field. Efudix cream, on the other hand, does treat a field but usually involves several weeks of red and inflamed skin. Aldara and Picato gel are limited by the amount of skin that can be treated at a time. None of these situations are ideal which is the reason why people often choose PDT. However, PDT is still a expensive.

Most prescriptions for Picato® gel & Aldara® are on a private prescription because PBS (Medicare) requires that the treatment is restricted to the face or scalp, and that other standard treatment is ‘inappropriate.’

Solar Keratosis may be difficult to control in some people. The starting point at home is moisturizer, sun protection and Vitamin B3 500mg twice per day.

Treatment of Solar Keratosis is worth the effort because of fewer sunspots and less skin cancer in future.

Treatment Comparison Table

The Rough Guide to Solar Keratosis Non-Surgical Treatment Options. Remember that many go away with simple daily sun protection!
EffectivenessTreatment ScheduleSide Effects SeverityDuration of Side EffectsCosmetic OutcomePriceTreatment Area
Efudix (5FU)Moderately effective2-4 weeks of twice daily applicationMarked1-2 weeks after stopping treatmentUsually Good$Large areas
PDT (Photodynamic Therapy) – clinicEffectiveone or two visitsModerate but can be painful1-2 weeksGood to Best$$$$Large areas
PDT (Photodynamic therapy) – daylightEffectiveone or two visitsMild to Moderate1-2 weeksGood to Best$$$Particularly good for the face and scalp
AldaraModerately Effective3x overnight applications per week for 4 weeksMarked1-2 weeks after stopping treatmentUsually Good$$Small – Maximum treatment area: 5cm by 5cm
Picato GelNew to the Market – moderately effective compared to placebo2 -3 days with once daily applicationsMarked7-10 daysShould be the same as Efudix or Aldara$$$Small – Maximum treatment area: 5cm by 5cm
Solaraze GelGenerally Not considered very effective3 months of twice daily applicationsMinimalTreatment DurationNeutral$Small to Moderate