Micronuclei as prognostic indicators in oral cytological smears: A comparison between smokers and non-smokers

Background: Micronucleus is a microscopically visible round or oval cytoplasmic chromatin mass in the extra nuclear vicinity, originated from aberrant mitosis, which consists of eccentric chromosomes that have failed to reach spindle poles during mitosis and are used as biomarkers for assessment of DNA damage. Micronuclei are characteristically seen in exfoliated cells of the buccal mucosa and urinary bladder wall in precancerous and cancerous conditions. Oral habits of smoking tobacco or chewing areca nut damage the oral tissues. An assessment of the damage is feasible by the detection of micronuclei in exfoliated cells of the oral tissues using smears. Objectives: The present study was designed to assess the presence or increase of micronuclei in buccal smears of individuals with tobacco habits against a control group of teetotalers. Materials and Methods: Two groups (smokers and non-smokers) of 50 individuals each were examined. Buccal smears of all participants were taken using cytobrush and stained with standard Papanicolaou′s (PAP) stain. Presence of micronuclei was assessed under Χ100 magnification and a count per 500 cells was determined. The results were analyzed statistically using t-test and Mann-Whitney test. Results: Smears of individuals with tobacco habits showed a significant increase in the total number of micronuclei per 500 cell counts. There was a definite correlation between the occurrence of micronuclei and the frequency and duration of smoking. A paradoxical age related increase in middle-aged groups was also observed. Conclusions: The genotoxic effects of tobacco smoke cause chromosomal damage in the epithelial cells of the oral mucosa and are reflected in the increased micronuclei in smokers. This is present even in the absence of clinically evident changes. This observation is vital in utilization of the micronuclei detection in smears as a prognostic, educational and interventional tool in the management of patients with smoking habits.