PER2 and melanoma: In particular, we intended to test the hypothesis that specific SNPs of the circadian clock genes, such as AANAT (arylalkylamine N-acetyltransferase), CLOCK (clock circadian regulator), NPAS2 (neuronal PAS domain protein 2), PER1 (period circadian clock 1), PER2 (period circadian clock 2), RORA (retinoic acid-related orphan receptor A), and TIMELESS (timeless circadian clock) could significantly influence the predisposition to develop cutaneous melanoma or the outcome of melanoma bearing patients.