The effect of MCPH1 c.904_916del mutation on the maintenance of genomic integrity and cancer predisposition is also supported by the significant increase in chromosomal rearrangements observed in the untransformed cells of the mutation carriers, and the tumor suppressor role of MCPH1 is reinforced by loss of wild-type allele in 40% of the MCPH1 c.904_916del mutation carrier breast tumors. The gene discussed is MCPH1; the disease is cancer.