Importantly, mosaic germline mutations, likely to have occurred early during embryogenesis, have been detected in multiple genes related to different disease conditions in affected individuals (see [191] for additional details), including tumor suppressor genes like TP53, RB1, genes involved in neurofibromatosis type-1 and -2, the Fanconi syndrome as well as BRCA1 [44, 156, 192–196]. The gene discussed is RB1; the disease is neurofibromatosis type 1.