p53 Expression as a Marker of Microinvasion in Oral Squamous Cell Carcinoma

Introduction: Oral squamous cell carcinoma (OSCC) has high local recurrence, partly caused by the lack of clear margin identification on surgical removal of cancerous tissues. Direct visualization by immunostaining and fluorescent in situ hybridization (FISH) in tissue sections gives more definite information about genetic damage at margins with appropriately selected biomarkers. Aims: To determine the usefulness of immunohistochemical techniques and FISH of the tumour suppressor TP 53 gene to identify microinvasion in marginal tissue sections and to relate the possible correlation between protein expression and genetic aberrations in OSCC cases in Malaysia. Methods: Immunohistochemistry and FISH of TP 53 genes were applied on 26 OSCC formalin fixed paraffin embed (FFEP) blocks selected from two oral cancer referral centers in Malaysia. Results: For p53 protein immunohistochemistry, 96% of the 26 OSCC studied showed positive immunostaining at the excision margins. In FISH assay, 48.9 +/- 9.7% of the cancerous cells were monoploid for p53 probe signals, 41.0 +/- 9.5 % were diploid, and 10.2 +/- 7.8 % were polyploid. A correlation between p53 immunostaining and TP53 gene aberrations was noted (p<0.05). Conclusions: Immunohistochemical analysis of p53 protein expression and FISH of TP53 gene could be applied as screening tool for microinvasion of OSCC.