Immunohistochemical pattern of P53 protein in human astrocytic tumors.

P53 immunohistochemistry in astrocytic tumors has usually been evaluated by the percentage of positive cells. However, in this study we analyzed the P53 immunopositive cells by their patterns of distribution. Formalin-fixed and paraffin-embedded sections from 38 patients with astrocytic tumors were examined. The distribution pattern of P53 immunostaining cells was divided into 3 types: negative, locally scattered, and diffuse clustering. There were 2 positive stains in 5 astrocytomas (40%), 12 positive in 24 anaplastic astrocytomas (50%), and 7 positive in 9 glioblastoma multiformes (78%). In astrocytomas, the positive cells were locally scattered. In anaplastic astrocytoma and GBM, the positive cells appeared locally scattered or as diffuse clustering. For the variant immunoreactive expression, the mean ages for patients with negative, locally scattered and diffusely clustered P53 immunostaining were as follows: 51.4, 52.6, and 28.4 years (P < 0.01), respectively. In anaplastic astrocytoma and GBM, the diffusely clustered pattern was more common in younger patients, whereas elderly patients in same groups tended to have few or no P53 immunopositive cells. Thus, our results implicate that clonal expansion of P53 immunopositive cells is associated with brain tumor progression.