KRT14 and squamous papilloma: We previously showed that mice expressing a tamoxifen-inducible Cre recombinase under the control of the cytokeratin 14 (K14) promoter, finally expressing an oncogenic mutation of K-ras (LSL-K-rasG12D mice), develop squamous papilloma in the oral cavity within 1 month from tamoxifen treatment [22].