In situ assessment of cell proliferation at the invasive front of oral squamous cell carcinomas.

In oral squamous cell carcinoma (OSCC) the histopathological malignancy grading of the invasive front has been found to offer the most reliable prognostic parameter. In the present study we compared such tumour front grading of 100 OSCCs with the in situ growth fraction demonstrated by MIB1 immunostaining following wet autoclave antigen retrieval. MIB1 labelling indices (LIs) were estimated both at the invasive front and in the central parts of OSCCs using two different evaluation methods (overall and random counting) to investigate whether MIB1 LIs represent a possible biological background for the tumour front grading. Statistically highly significantly increased MIB1 LIs were found at the invasive tumour fronts with both counting methods compared with the centres of the same tumours. For LI estimation the classic overall counting procedure proved to be superior. However, in contrast to tumour front grading, MIB1 LIs revealed no correlation with the clinical outcome of the patients concerned. Our results demonstrate that the invasive tumour front of an OSCC is composed of (a) tumour subpopulation(s) with higher proliferative activity. However, determination of the proliferative activity by MIB1 of this tumour area offers no prognostic information.