Pediatric glioblastomas: a histopathological and molecular genetic study

Abstract

Glioblastoma multiforme (GBM) occurs rarely in children. Relatively few studies have been performed on molecular properties of pediatric GBMs. Our objective in this study was to evaluate the genetic alterations in pediatric GBM (age < or = 18 years) with special reference to p53, p16, and p27 protein expression, alterations of the epidermal growth factor receptor (EGFR), and deletion of the phosphate and tensin homolog gene (PTEN). Thirty cases of childhood GBMs reported between January 2002 and June 2007 were selected, and slides stained with hematoxylin and eosin were reviewed. Immunohistochemical staining was performed for EGFR, p53, p16, and p27, and tumor proliferation was assessed by calculating the MIB-1 labeling index (LI). Fluorescence in situ hybridization analysis was performed to evaluate for EGFR amplification and PTEN deletion. Histopathological features and MIB-1 LI were similar to adult GBMs. p53 protein expression was observed in 63%. Although EGFR protein overexpression was noted in 23% of cases, corresponding amplification of the EGFR gene was rare (5.5%). Deletion of the PTEN gene was also equally rare (5.5%). One case showed polysomy (chromosomal gains) of chromosomes 7 and 10. Loss of p16 and p27 immunoexpression was observed in 68% and 54% of cases, respectively. In pediatric de novo/primary GBMs, deletion of PTEN and EGFR amplification are rare, while p53 alterations are more frequent compared to primary adult GBMs. Frequency of loss of p16 and p27 immunoexpression is similar to their adult counterparts. This suggests that pediatric malignant gliomas are distinctly different from adult GBMs, highlighting the need for identification of molecular targets that may be adopted for future novel therapeutic strategies.

Fig. 1

Hematoxylin and eosin staining. (a) Photomicrograph of a glioblastoma showing brisk mitotic activity. (b) Typical pallisading necrosis. (c) Glioblastoma with endothelial proliferation. (d) A case showing bizarre multinucleated tumor giant cells. Original magnification, ×200 for a–d.

Fig. 2

Immunohistochemical staining. (a) A case showing very high proliferation activity as demonstrated by immunoreactivity to MIB-1. (b) Immunohistochemistry for p53 showing strong (4+) nuclear immunoreactivity. (c) Diffuse membranous expression of epidermal growth factor receptor in tumor cells. (d) A case showing loss of expression (negativity) of p16 protein. (Inset) Same case showing negativity for p27 protein. Original magnification: ×200 for a–c and d inset; ×100 for d.

Fig. 3

Fluorescence in situ hybridization analysis. (a) A case with tumor cells expressing normal phosphate and tensin homolog protein (PTEN; two red signals per cell) and CEP10 (two green signals per cell). (b) Photomicrograph of a tumor showing hemizygous deletion of 10q23/PTEN locus: a single red signal in most of the tumor nuclei (PTEN) and paired green signals for CEP10. (c) Normal EGFR/CEP7 expression (two red and two green signals in most of the tumor cells). (d) Section from a tumor showing EGFR amplification. Innumerable red signals (EGFR) are seen compared to few green signals (CEP7). (e) Section of a tumor showing polysomies (chromosomal gain). Original magnification, ×1,000 for a–e.