The invention discloses in vitro methods and a system for determining a predisposition of a subject for developing a cancer on the basis of analyzing a sample of the subject for an alteration of at least one allele of the RAD51C gene. Further disclosed are in vitro methods for assessing clinical features or a pathological progression of a cancer and for assessing at least one RAD51C gene alteration in a cell. In addition a kit for determining a predisposition of a subject for developing a cancer, and certain uses of oligonucleotides for determining the presence of at least one mono-allelic germ-line mutation of the RAD51C gene.