Other genes or their protein products, as Rb, p53, BRCA2 (breast cancer susceptibility) and PRAD1 (cyclin D1/PA 1 oncogene) [47, 103–105] have been linked with PC, although none of them could consistently and reliably distinguish between benign and malignant disease [105]. The gene discussed is BRCA2; the disease is pachyonychia congenita.