Association of Micronuclear Frequency with Dysplasia and Cytogenetic Changes (p53 Mutation and p16 Expression) in Oral Potentially Malignant Disorders

Abstract

Aims: The present study evaluated the frequency of micronuclei in oral potentially malignant disorders (OPMDs) and their association with the presence of dysplasia on cytology and biopsy as well as their association with p53 mutation and p16 expression. Cytological findings of dysplastic changes in OPMDs were compared to histological diagnoses.

Material and methods: This was a cross-sectional, observational, descriptive study. Scrape smears (n = 74) were collected from lesions in patients with OPMDs. Punch biopsy was collected in patients showing dysplastic changes. Tissue microarray for p53 mutation and p16 expression was performed using paraffin embedded blocks. Cases were classified into grades of dysplasia using both scrape smears and biopsy. Micronuclei frequency was calculated per 100 cells using scrape smears. Mann-Whitney U test was used for correlation of cytology and histology for grade of dysplasia as well as micronuclear frequency with p53 mutation and p16 expression.

Results: Micronuclear frequency was found to be increased in patients with dysplasia. A significant association of micronuclear frequency with dysplastic changes was seen on cytology. Sensitivity of cytological evaluation was found to be 64.7%. The association of the micronuclear frequency of samples with p53 mutation and p16 expression was nearly significant (n = 28, P = 0.069 and 0.095, respectively).

Conclusion: Micronuclear frequency can be a reliable marker of mutagenic change in OPMDs. Cytological assessment of micronuclei can serve as useful, non-invasive, and relatively inexpensive tool to predict cancerous changes in OPMDs.

Keywords: Micronuclei; OPMD; p16 expression; p53 mutation.

Figure 1

Smear showing 6 microneuclei in a cell (PAP, 40×)

Figure 2

A case of dysplasia on scrape smears with cells showing high N/C ratio, nuclear hyperchromasia and nuclear polymorphism (H/E, 40×)

Graph 1

Receiver operating characteristic curve for association of micronuclear frequency with cytological diagnosis of dysplasia under the non-parametric assumption. Area under curve: 0.763; Asymptotic Sig. (P) < 0.001. Red Circle indicates optimal cut off point as per Youden’s index at the sensitivity value 0.744 and 1-specificity value of 0.296

Figure 3

A case of well differentiated squamous cell carcinoma which was p53+ve (40×)

Figure 4

A case of squamous cell carcinoma positive for p16(40×)