However, as the tissue sections also contain normal cells, and precise estimation of tumour cell content is difficult [28], it is likely that potential differences remain undetected in a background of normal cells expressing DAPK1. In addition, it is likely that the tumour cells are heterogeneous with respect to DAPK1 methylation and expression, which would also confound the expression analysis. This evidence concerns the gene DAPK1 and neoplasm.