Tumors with poorly defined transition areas between healthy skin and tumor cells, corresponding by extrapolation to the field cancerization of squamous cell carcinoma/actinic keratoses, often require specific immunohistochemistry studies (S-100, Sox-100, PRAME) in melanoma [41] and cytokeratin 7 in EMPD [42]. This evidence concerns the gene KRT7 and squamous cell carcinoma.