We have shown that WDPM are genetically distinct from malignant mesotheliomas and in our hands have a characteristic pattern of C > A transversion substitution mutations; EHD1, FBXO10, CHD5, MAGED1, ATM, and TP73 missense mutations; as well as enrichment of COSMIC mutation signature 24. This evidence concerns the gene CHD5 and well differentiated papillary mesothelioma.