Pathology

1. Solar keratosis: squamous cell carcinoma in situ
   • AKA senile or actinic keratosis
2. Histological appearance include
   • Hyperkeratosis (thickening of the keratin layer)
   • Focal parakeratosis
   • Irregular acnathosis (thickening of the prickle layer)
   • Basal layer atypia only
3. Risk of progression to malignancy: 25% if untreated

Approach

• Examine as for any lump

1. Inspection
   • Usually multiple
   • Yellow-grey or brown in colour
   • Begin with thickening of the skin which can become unsightly and catch on clothing
   • Scaly surface
   • Can occur as a "solar horn" on the pinna or the ear
2. Palpation

Completion

1. Ask about similar lesions elsewhere
2. How the lesion affects life 

Treatment:

1. Non-surgical
   • Cryotherapy
   • Topical application of 5-FU (fluorouracil)
   • Retinoic acid (to reverse the damaging effects of sunlight)
2. Surgical
   • Shaving off affected skin