Comparative Evaluation of Immunohistochemical Expression of p16 with p16 Microsatellite Marker by PCR in Surgical Margins of Oral Squamous Cell Carcinoma

Oral squamous cell carcinoma (OSCC) is most common oral cancer with multifactorial etiology. Surgical therapy is treatment of choice but known to have recurrence. The main reason for recurrence is associated with surgical margins which need to be tumor free. Changes at genetic level cannot be ascertained only through routine light microscopy in surgical margins, even though they are tumor free. Detection of early marker like p16 can help in predicting the risk of recurrence. Hence study aimed to detect p16 microsatellite marker (D9s1747) in surgical margins of oral squamous cell carcinoma and compare the same with p16 marker through immunohistochemistry. Total of 40 paraffin embedded tissue samples diagnosed and surgically treated cases of OSCC were included. From each sample one tumor proper and one surgical margin was obtained. From paraffin embedded tissue sample 2 sections of 4 µm thick was obtained from tumor proper and tumor margin. One section was stained with hematoxylin and eosin and other section was stained immunohistochemically using p16 antibody. DNA extraction was done for tumor proper and surgical margin tissue and PCR analysis was carried for p16 microsatellite marker (D91747). Out of 40 cases 37 cases showed positivity in tumor proper for p16 with IHC. Out of 37 cases 23 cases showed positivity for both tumor proper and surgical margin. There were 3 cases negative for tumor proper. Out of these 3 cases, 1 (33.3%) case was positive for surgical margin. Out of 40 cases 27 cases showed positivity for tumor proper with p16 microsatellite marker. Out of 27 cases 16 cases showed positivity for both tumor proper and surgical margin. There were 13 cases negative for tumor proper. However there were 8 (61.5%) cases negative which were in tumor proper but showed positivity for surgical margin. Other 5 cases were negative in both tumor proper and surgical margin. Our study reveals that surgical margins of OSCC exhibit alteration in p16 markers both by IHC and PCR techniques. p16 and p16 microsatellite marker detection in margins indicates field change. Further studies with larger sample size comparing expression with clinical and histological parameter and follow up has to be done to substantiate our findings.