Huge Bowen's disease: a pitfall of topical photodynamic therapy.

Bowen's disease (BD) is one of the major histological types of nonmelanoma skin cancer. With challengeable "multiple and large" patches of BD, topical photodynamic therapy (PDT) has been considered as a first-line effective modality for decades. However, there was no general consensus among authors about the definition of "large BD". Herein, we have experienced two cases of huge BD which has over 10 cm in diameter with resistance to topical PDT. Our cases suggest that topical PDT is likely to show a much less satisfactory effect for huge BD than we have expected, and the previously specified indication of topical PDT ("multiple, larger lesion") seems the fallacy of hasty generalization. Therefore, it is required that further cut-off value of size for suitable candidate for topical PDT would be clarified.