Combination therapy for perianal squamous cell carcinoma in situ with imiquimod and photodynamic therapy.

Perianal squamous cell carcinoma in situ (SCCIS) is a relatively rare intraepidermal neoplasm that has the potential to progress to invasive squamous cell carcinoma. First-line treatment is surgical excision, though nonsurgical treatment modalities such as 5-aminolevulinic acid-based photodynamic therapy (ALA-PDT) and imiquimod also have been investigated for this neoplasm. Unfortunately, recurrences are known to occur after both surgical and nonsurgical monotherapies. We report a case of perianal SCCIS that was successfully treated with a novel combination of ALA-PDT and imiquimod.