*2.1. Study Participants*

We have conducted a study on 40 consecutive patients with cSCC, 28 consecutive patients with AK and 40 healthy subjects as controls, with skin phototypes I–IV. The patients and controls were matched by age and sex. In the control group, we included healthy subjects who addressed the dermatology clinic for disorders such as skin tags or nevi, disorders that do not interfere with our determinations. In all cases, the diagnosis was confirmed histopathologically. Informed consent was obtained from all study participants. The procedures and experiments were conducted according to the Declaration of Helsinki. The study protocol was approved by the Ethics Committee of the Victor Babes Infectious and Tropical Diseases Hospital (3/10.03.2018).
