Method of detecting a mutational signature in a sample

The present invention provides a method of detecting mutational signatures in a DNA sample. The invention relates to method of detecting signatures arising from rearrangements in the DNA in the sample and determining the contributions of known rearrangement signatures to said rearrangements. In particular embodiments, the contributions are determined by computing the cosine similarity between the rearrangement mutations in said catalogue and the rearrangement mutational signatures. The rearrangement signatures are classified based on whether they are clustered or not, whether they are tandem duplications, deletions, inversions or translocations and on the basis of their size.