[1827] IMP3 Expression in Astrocytic and Oligodendroglial Tumors

Larry Zhao, Thomas W Smith, Di Lu, Hongbo Yu, Lan Qin, Kaycee Y Xiao, Karen Dresser, Thomas Stockl, Bruce A Woda, Zhong Jiang, Suyang Hao. University of Massachusetts Medical School, Worcester, MA

Background: Insulin-like growth factor-II mRNA-binding protein 3 (IMP3), an oncofetal protein, is involved in embryogenesis and is expressed in multiple malignant neoplasms. IMP3 has been shown to have higher expression in high grade tumors and is associated with poor prognosis. With the exception of glioblastoma, IMP3 expression in primary brain tumors of glial origin has not been systematically investigated. In this study, IMP3 expression in a series of astrocytic and oligodendroglial tumors is examined and correlated with histologic type and WHO grade.
Design: Two hundred forty-four (244) cases of neurosurgical biopsy and brain resection specimens from 1998-2008 were retrieved from the pathology archives of our institution. The tumors included: 149 cases of glioblastoma (GBM), (WHO Grade IV); 19 anaplastic astrocytoma (Grade III); 35 anaplastic oligodendrogliomas and anaplastic mixed gliomas (Grade III); 14 oligodendrogliomas and low grade mixed gliomas (Grade II); and 17 pilocytic astrocytomas (Grade I). Ten cases of gliosis were used as controls. All cases were stained with a monoclonal antibody specific for the IMP3 protein, and evaluated independently by 3 observers. IMP3 expression was divided into 2 categories: positive (moderate or strong cytoplasmic staining with membranous accentuation, >5%) and negative (absent or weak cytoplasmic staining, <5%).
Results: IMP3 was expressed in 93% (138/149) of GBMs, 79% (15/19) of anaplastic astrocytomas, 26% (9/35) of anaplastic oligodendrogliomas and anaplastic mixed gliomas, and 18% (3/17) of pilocytic astrocytomas. Grade II oligodendroglioma and low grade mixed gliomas (0/14), and gliosis (0/10) showed no IMP3 expression. This expression was statistically significant (p < 0.05) between the high grade tumors and gliosis, among the high grade tumors (Grade III and IV), and additionally between each of the high grade tumors and low grade tumors. Among the low-grade (Grade I and II) tumors and gliosis cases, no statistically significant difference in IMP3 staining was found.
Conclusions: IMP3 expression is positively correlated with WHO grade. IMP3 expression is found in the majority of GBMs (Grade IV). Grade III gliomas have a higher percentage of expression than Grade I and II gliomas. IMP3 is expressed more frequently in astrocytic tumors compared to oligodendroglial tumors of the same grade or even higher grade. IMP3 staining is helpful in distinguishing high grade gliomas from low grade ones and gliosis.
Category: Neuropathology

Tuesday, March 20, 2012 1:00 PM

Poster Session IV # 248, Tuesday Afternoon


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