Squamous cell carcinoma of the skin is a common malignancy in fair skinned individuals, particularly in areas of high sun exposure. Two important precursor lesions, actinic keratosis (dysplasia) and carcinoma in situ (Bowen's disease) are also of significant importance.
Frequently, squamous cell carcinoma will arise in an area of dysplasia.
Natural History of Actinic Keratosis (dysplasia)
Actinic keratosis is the precursor lesion of SCC. They may progress to SCC in 10-20% of cases, but may also regress. It is estimated that there is an 0.1% yearly risk of transformation per lesion.
Natural History of Bowen's Disease (SCC In Situ)
Like actinic keratosis, Bowen's Disease does not always progress to invasive SCC. They may expand to cover a large area of skin, although these lesions are more frequently invasive.