The proliferative potential of the astrocytoma : the relation between Ki-67 and histopathologic criterias

Abstract EN

Background : Astrocytic tumors are the most common primary CNS tumors.

The grading of the astrocytomas has been traditionally relied on histologic assessment, but sometimes its still a subject of debate.

This study used MIB-1 monoclonal antibody, a proliferative marker that can be used in formalin fixed paraffin embedded tissue to evaluate its capability for differentiating between different grades of astrocytomas. Patients and Methods : Ninety cases of low grade astrocytoma, anaplastic astrocyloma and gliboblatoma (30 cases of each) were selected from total 236 cases of astorcytomas during a period of 1994 to 2003.

Histologic grading of the tumors was performed based on WHO classification.

The proliferative potential of the tumors was estimated by counting mitosis and using the MIB-1 Ll performed on paraffin sections.

Variety of analysis methods were used to evaluated difference in MIB-1 Ll between the tree groups. Results : The mean MIB-1 Ll was 10.13 (range: 1 to 63) in low grade astrocytomas 48.75 (range: 2 to 366) in anaplastic astrocytoma and 238 (range: 6 to 532) in glioblastoma.

The mean of mitotic count was 0.133 (range: 0-3), 2.93 (range: 0-23) and 11.66 (range: 1 to 34) in 1000 counted unclei in low grade astrocytomas, anaplastic astrocytoma, and glioblastoma respectively.

Multivariate analysis showed that after omission of effect of age which was significantly higher in glioblastoma, there is a meaningful difference between mean of MIB-1 Ll of the three groups (P < 0.000). Conclusion : This study suggests that MIB-1 Ll can be used as an adjuvant to histopathogic grading for proper diagnosis and grading of astorcytomas especially in borderline cases and small biopsies.

Due to high heterogencity of this value, determination of cut off point is impractical.