Epithelial-to-mesenchymal transition contributes to invasion in squamous cell carcinomas originated from actinic keratosis through the differentiated pathway, whereas proliferation plays a more significant role in the classical pathway.

Epithelial-mesenchymal transition participates in transformation from AK I into iSCC (differentiated pathway), whereas a higher proliferative capacity facilitates intraepidermal extension in the classical pathway. Podoplanin, which is also involved in tumour invasion, does not seem to play a differential role in either pathway. Finally, the absence of differences in p53 and p16 expressions is at variance with other epithelia where the classical pathway is associated with human papillomavirus infection and can be explained by the fact that both AK pathways share identical mechanisms of actinic oncogenesis.