PIK3CA and Merkel cell skin cancer: In addition, MLH1 (22/65, 33.85%, p = 2.63E-13), MSH2 (25/65, 38.46%, p = 2.87E-07), MSH6 (28/65, 43.1%, p = 1.01E-11), PMS2 (12/65, 18.5%, p = 3.79E-03), and POLE (28/65, 43.08%, 5.39E-08) mutations were more common in the MCC cohort than the TCGA PCA, while mutation frequency in PTEN, PIK3CA, and TP53 were not statistically difference in the two datasets.