MT-ND4 and neoplasm: Patient 0504 showed the highest number of viral integrations in mtDNA, with 12 different integration sites in the tumour sample (3 in RNR2, 2 in ND4, 2 in ND5, 1 in ND1, 1 in ATP6, 1 in CYTB, and 2 in the D-loop region) and 1 in the non-tumour tissue sample (in the D-loop region) (Fig. 3, Table 3 and Supplementary Data 3).