Rapidly-growing squamous cell carcinoma shortly after treatment with ingenol mebutate for actinic keratoses: report of two cases.

Actinic keratoses (AKs) are defined as cutaneous areas of atypical squamous transformation that are regarded as an early step in the continuum of alterations leading from normal skin to invasive and metastatic squamous cell carcinoma (SCC). AKs are classified as precancerous lesions by some authors and in situ SCC by others. The rate of evolution of a given AK to an invasive SCC has been estimated as 0·075-0·096% per lesion per year. These rates are similar to those estimated for gynaecological intraepithelial neoplasia. We describe two cases of SCC with rapid onset that developed after the application of ingenol mebutate gel for the treatment of AKs.