A CG > TG substitution-enriched signature (designated as “Signature A”) was the most common form in the 14 FL tumours, and the third most common form (designated as “Signature C”) was similar to signature 9 categorized by COSMIC; these signatures were considered to be associated with AID and error-prone polymerase η activities characterized by a T > C/G transition in the NpTpA/T context (Fig. 4a and Supplementary Fig. S4a,b). Here, AICDA is linked to neoplasm.