Detection of damage to the mitochondrial genome in the oncocytic cells of Warthin's tumour

Warthin's tumour of the salivary glands is composed of oncocytic cells containing excessive numbers of mitochondria which show frequent structural abnormalities and reduced metabolic function. Recent evidence of a strong association between cigarette smoking and the occurrence of Warthin's tumour prompted this study, to look for evidence of damage to mitochondrial DNA (mtDNA) that could be the result of an increase in oxidative stress; two-colour fluorescence in situ hybridization (FISH) was developed to show the distribution of mitochondria with deleted mtDNA in paraffin wax-embedded material. Approximately 10% of mtDNA bears the 'common' 4977 bp deletion. Using the polymerase chain reaction (PCR), the 4977 bp deletion was further quantified, in Warthin's tumour and age-matched normal parotid control tissue. Whilst the deletion was present in all parotid tissue, its presence was significantly higher in oncocytic tumour cells. In a small number of controls, there was a trend towards higher concentrations of the deletion in smokers.