OSCE — rough sun-damaged patches: actinic keratosis field care and SCC red flags

Brief (to candidate)

A 71-year-old fair-skinned man has multiple rough, gritty, erythematous scaly patches on the bald scalp and dorsal forearms that are “easier to feel than see.” One scalp plaque has thickened and become tender over 6 weeks. He has cumulative outdoor sun exposure. You have 8 minutes to diagnose, stratify field disease, plan treatment, and recognise SCC red flags.

Candidate instructions

1. Recognise actinic keratosis (AK) and place it on the AK → Bowen → invasive SCC spectrum.
2. Explain field cancerization and why multiple lesions matter.
3. Distinguish lesion-directed vs field-directed therapy options.
4. Identify red flags requiring biopsy (thickening, ulceration, pain, treatment failure).
5. Mention photoprotection and optional chemoprevention concepts (e.g. nicotinamide evidence).
6. Safety-net for actinic cheilitis / cutaneous horn.

Examiner checklist (mark each domain / 10)

Model key actions

• Diagnose multiple AKs with field cancerization and treat both individual lesions and the field.^[1][2]
• Escalate the tender thickened scalp plaque for biopsy rather than further blind cryotherapy.^[6]
• Photoprotection, surveillance, and realistic expectations of field therapy inflammation.^[3]

Common errors

• Calling all scaly sun spots “dry skin” without considering AK.
• Cryotherapy only while ignoring field therapy for dozens of lesions.
• Observing a thickening/tender AK without biopsy for invasive SCC.
• Missing actinic cheilitis risk on the lower lip.
• Overpromising “cure forever” without follow-up for new AKs/SCC.