Finally, signatures of uncertain and speculative origins (Alexandrov et al., 2018) were also observed, including SBS17a-b in gastric and esophageal models; SBS18, potentially due to reactive-oxygen-species-induced DNA damage, in neuroblastoma cell lines; SBS9, which might result from aberrant processing of AID-induced cytidine deamination by polymerase η, in lymphoma cell lines; and SBS28, SBS34, SBS39, and SBS40, which were found mainly in the cancer types in which they had been previously reported. This evidence concerns the gene AICDA and neuroblastoma.