Are solar keratoses
dangerous?
In themselves, solar keratosis are not cancerous and do no harm. But,
they can sometimes be unsightly. Also, up to about a
quarter of solar keratosis will clear away by
themselves without any treatment over the course of
one year.
However, in people who have between seven and eight
solar keratosis on their skin, there is about a 1 in
10 chance that one will turn into a form of skin
cancer called squamous cell carcinoma over a 10 year
period. This is not the most serious form of skin
cancer. It is a fairly slow growing cancer and can
usually be easily cured if treated early enough.
How are solar
keratosis diagnosed?
Your doctor may be
able to diagnose a solar keratosis by its typical
appearance alone. However, sometimes this may be
difficult. You may be referred to a dermatologist
and/or your doctor may suggest that a skin biopsy is
taken. This is where a small sample of your skin is
taken and examined under the microscope in a
laboratory.
There was a study done
that was aimed to describe the prevalence and
incidence of solar keratosis and skin cancers and the
natural history of solar keratosis in a random
population sample. It was a cross-sectional study,
with follow-up, conducted in South Wales, and involved
1034 subjects aged 60 years and over drawn from the
Family Health Services Authority register. The main
outcome measures were detection of the presence of
solar keratosis and skin cancers on sun-exposed skin
and photographic validation of solar keratosis and
biopsy confirmation of cancers wherever possible. We
found that solar keratosis prevalence was 23% (95%
confidence interval 19.5-26.5) and that of skin cancer
(all types) 2% (95% confidence interval 1.0-3.5). The
incidence rate of solar keratosis was 149 lesions per
1000 person-years and of non-melanoma skin cancer 9
per 1000 person-years. In all 21% (95% CL 16-26) of
solar keratosis regressed spontaneously during
follow-up. None underwent malignant change. We believe
that the failure of individuals to seek medical advice
and the variable under-registration of non-melanoma
skin cancer makes population-based study important.
The high prevalence and incidence of malignant and
pre-malignant skin lesions in this random sample raise
major public health concerns. The high rate of
spontaneous regression of solar keratosis and the low
rate of malignant change challenges conventional views
about the need for routine treatment of these lesions.
