EXPRESSION OF P53 IN OLIGODENDROGLIOMAS

The expression of the nuclear protein p53 in oligodendrogliomas was in vestigated by immunohistochemistry, using a monoclonal anti-p53 antibo dy (DO-7) on formalin-fixed, paraffin-embedded material in 84 histolog ically verified cases, and compared with the histopathological grade a nd survival. p53-immunoreactive cells were found in 75 per cent of the samples acquired at the first biopsy. The p53 labelling index was not related to the degree of nuclear anaplasia. Tumour cases with more th an 75 per cent p53 immunostained cells had a rapidly fatal clinical co urse. However, no significant correlation was found between p53 labell ing index and tumour grade, mitotic index, or ploidy status. In most t umour recurrences (n=25), the p53 labelling index increased or remaine d at the level of the first biopsy. In five cases (6 per cent), p53 wa s absent in the first sample as well as in the recurrence. Irrespectiv e of the underlying aberration of either the gene or the metabolic pat hway of p53, it is concluded that a high percentage (i.e., more than 7 5 per cent) of p53-immunolabelled cells is predictive of an unfavourab le clinical course, while a percentage lower than 75 per cent immunore active cells does not exclude a rapid fatal outcome.