PIK3CA and Merkel cell skin cancer: The most common genomic aberrations in patients with Merkel cell carcinoma were in the TP53 gene and the cell cycle pathway (CDKN2A/B, CDKN2C or RB1), followed by the PI3K/AKT/mTOR pathway (AKT2, FBXW7, NF1, PIK3CA, PIK3R1, PTEN or RICTOR) and DNA repair genes (ATM, BAP1, BRCA1/2, CHEK2, FANCA or MLH1).