APOBEC3B and neoplasm: Having determined that APOBEC3A is expressed during the terminal differentiation of non-cancerous epithelial cells in the tonsil and oesophagus, and that this expression pattern could be recapitulated in immortalised but non-transformed epidermal keratinocytes in culture, we next investigated APOBEC3A and APOBEC3B expression patterns in scRNA-seq data from tumour samples.