In addition to selective pressures and mesoscale features, additional factors are likely to influence the APOBEC3-attributable fraction of an overall tumor mutational landscape including whether A3A and/or A3B is expressed, expression levels, duration of expression, intrinsic activity, and accessibility of chromosomal DNA (replication stress, R-loop levels, chromatin state, etc.). The gene discussed is APOBEC3B; the disease is neoplasm.