[1640] Are There Any Differences in the Expression of IDH1 and P53 Proteins between Astrocytoma and Oligodendroglioma?

Mei Zheng, Suash Sharma. Medical College of Georgia, Augusta

Background: Isocitrate dehydrogenase 1 (IDH1) mutation has been well-described in diffuse glioma in recent large studies, with a reportedly similar frequency in astrocytomas and oligodendrogliomas. We compared the expression of IDH1 and p53 in diffuse gliomas to assess any differences between astrocytoma and oligodendroglioma of different grades.
Design: A total of 27 glioma cases were studied, including 20 astrocytomas, 4 oligodendroglioma, 2 anaplastic ependymoma, and 1 ganglioglioma. Autopsy brain tissue with reactive gliosis were used as control. Immunohistochemical staining using IDH1 and P53 antibodies was performed. The percentage positivity of tumor cells showing granular cytoplasmic staining was scored as 1 to 4 (0-25, 26-50, 51-75,76-100%), and staining intensity scored as 1 to 3 (low, medium, strong). A numerical IHC score for each case was derived by multiplying the percentage positivity score with intensity score.
Results: IDH1 immunopositivity was granular cytoplasmic, and seen in 7 of 20 astrocytomas of all grades (35%). Grade-wise distribution was as follows: glioblastoma (1/6), anaplastic astrocytoma (2/6), astrocytoma grade 2 (4/5) and grade 1 (0/3). In contrast, all 4 oligodendrogliomas (100%) showed diffuse strong staining (3 grade-2, and 1 grade-4). No staining was observed in ependymoma (2), ganglioglioma (1) or reactive gliosis (9). IDH1 staining was much more intense in oligodendroglioma as compared with the majority of astrocytomas (p=0.0003). The expression of IDH1 and p53 proteins in 7 astrocytoma cases was similar (t-test, p=0.446), whereas the pattern was reversed in 3 oligodendrogliomas with high expression of IDH1 but low p53 protein (p=0.003).
Conclusions: Our study supports the observation that IDH1 may be an early event in the development of diffuse glioma, and further shows that IDH1 likely contributes more to the tumorigenesis of oligodendroglioma than astrocytoma, in contrast to p53. IDH1 is neither expressed in reactive gliosis nor in majority of glioblastomas. Therefore IDH1 alongside p53 carries the potential to be a diagnostic marker of low-grade diffuse glioma.
Category: Neuropathology

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 227, Tuesday Afternoon

 

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