[1499] 1p and 19q FISH Study of the Glioblastomas

B Kim, JK Myung, SJ Byun, SH Park. Seoul National University College of Medicine, Seoul, Republic of Korea

Background: The fluorescence in situ hybridization (FISH) of the 1p/19q used to be evaluated by the ratio of the numbers of red spots and the green spots(deletion: the ratio <0.8). Recently, however, Nagasaka et al. applied the evaluation guideline for neuroblastoma for investigating 1p/19q FISH status of the glioblastoma (GBM). By the guideline for neuroblastoma, the deletions by the ratio (<0.8) include definitive deletion, disproportional deletion and imbalance and the normal ratio of 1p/19q (ratio: 1) include true normal, monosomy or polysomy. The purpose of the present study is to verify the 1p and 19q status of 52 cases of GBMs. Serving as the control were 30 cases of anaplastic oligodendrogliomas.
Design: We performed a clinicopathologic review as well as immunohistochemical (GFAP, p53, EGFR, EGFRvIII, PTEN, MGMT, galectin-3 and MIB-1) and molecular studies (EGFR FISH, 1p19q deletion FISH, MGMT MSP) to characterize 1p and/or 19 abnormal GBMs.
Results: Using the simple ratio <0.8, 1p and19q deletions were 25% (13/52), and 19.2% (10/52) of GBMs, respectively, which included a 7.7% (4/52) of co-deletion. However, with the guideline for neuroblastoma, true 1p deletion was 15.3% (8/52), true 19q deletion was 13.4% (7/52) and 1p/19q co-deletion was 5.8% (3/52), which included definitive deletion and disproportional deletion. The remaining 5 cases (9.6%) of 1p deletion and 3 cases (5.8%) of 19q deletion by ratio were imbalanced. When they were evaluated by ratio, there were no statistically significant immunohistochemical and molecular markers of the above mentioned parameters to characterize 1p and/or 19q detected GBMs except MGMT MSP and galectin 3; there was more MGMT MSP positivity (5/6, 83.3%) in 19q deletion and less galectin 3 protein expression in 1p and/or 19q deleted group (p<0.05). When they were evaluated by the guideline for neuroblastoma, 1p/19q deleted group showed male predominance and lower galectin-3 expression (p<0.05). In the Kaplan Meier survival analysis, there was no significant survival difference between 1p/19q deleted and non-deleted groups evaluated by any evaluation methods. However, anaplastic oligodendroglioma with 1p and/or19q deletion showed a significantly higher true deletion (78.6%) than glioblastoma (42.1%) (p=0.011).
Conclusions: From our study, we could not find any significant immunohistochemical or molecular markers to characterize 1p/19q deleted GBM except MGMT-MSP and galectin-3. In order to identify a more accurate status of 1p/19q, the guideline for neuroblastoma appears to be more appropriate than an evaluation just by ratio.
Category: Neuropathology

Tuesday, March 10, 2009 9:30 AM

Poster Session III # 196, Tuesday Morning