This image shows a cutaneous papilloma generated in a 'two stage' mouse model of skin cancer formation. These papilloma lesions have a high risk of developing into squamous cell carcinoma, the second most common form of skin cancer. The Anti-Keratin 5 protein (red) identifies the keratinocytes within the lesion. Cell nuclei are stained with DAPI (blue). The image shows that the transcription factor DLX3 (green) is expressed by the most keratinized and differentiated cells, also called