Are actinic keratoses really squamous cell cancer? How do we know if they would become malignant?

Actinic keratosis (AK) is a very common skin disease caused by chronic sun exposure. AKs have historically been characterized as being “precancerous” or “premalignant.” It is true that these lesions do not possess metastatic potential, because they are confined to the epidermis, but it is not accurate to deem them “premalignant.” AK qualifies as a malignant neoplasm, because it also fulfills criteria for malignancy in classic pathology, namely, the capability, or potential, to kill by either destruction of tissue locally or by metastasis widely. In this context, AK is considered now by many a carcinoma in situ and can persist or progress to invasive squamous cell carcinoma (iSCC), which rarely metastasizes. Through this controversy, which speaks to an issue we have been debating for at least a century, we should like to start a constructive debate to reach a unanimous conclusion considering the various theories and points of view in the literature.