Comment on 'The detection rate of Human Papillomavirus (HPV) in well differentiated squamous cell carcinoma and keratoacanthoma: is there new evidence for a viral pathogenesis of keratoacanthoma?' - Reply from authors.

We fully agree with the authors that there is lack of validated histopathological criteria that allow to accurately differentiate well-differentiated SCC from KA. For this reason, we believe that both terms should be best avoided in the future. Therefore, we recently proposed a novel classification system, which simply differentiates whether the tumors arise within a field of cancerization and or in the absence of field cancerization. [2] We consider the former as true carcinomas with a low but existing metastatic potential.