AICDA and plasma cell myeloma: Furthermore, we found two additional signatures so far not implicated in myeloma: the noncanonical AID (Signature #9), contributing to 28% of all substitutions (range: 17–55%), and a fourth compatible with signature #8, accounting for 28% of all substitutions (range: 13–45%), previously described in different cancers and pertaining to a yet unknown mutational process (Fig. 4b)23,29.