History:

40 year-old man noted the recent onset of a red, scaly and asymptomatic patch on the upper arm. The patient was an avid swimmer and owned a home pool. He denied use of sunscreen. Differential diagnosis included superficial basal cell carcinoma and squamous cell carcinoma in-situ. Biopsy disclosed SCCIS (or Bowen;s Disease). Treatment consisted of 5% imiquimod applied daily for 8 weeks (off-label use).