A 56-year-old woman sought medical attention for an asymptomatic lesion on the thigh.
Key point: Physical examination revealed a 1.3 by 0.9-cm red and scaly patch on the dorsum of the left thigh. The differential diagnosis includes squamous cell carcinoma in situ (Bowen disease), superficial basal cell carcinoma, and lichenoid keratosis (an inflammatory variant of seborrheic keratosis). Biopsy showed in situ squamous cell carcinoma.
Treatment: Treatment consisted of once-daily topical application of 5% imiquimod until erosion occurred (12 weeks). The lesion went on to heal uneventfully.
Note: Imiquimod treatment for squamous cell carcinoma in situ is off-label. However, it does afford an excellent cosmetic result compared with surgical intervention.