BRCA1 and pachyonychia congenita: Biomarker enrichment for the POLO trial was based on the presence of germline BRCA1 and BRCA2 mutations identified using the BRACAnalysis companion diagnostic assay; however, germline BRCA1 and BRCA2 mutations, which are typically found, respectively, in 1% and 2% of unselected PC cases, might reflect only the tip of the iceberg with regard to the potential target population [42].