Assessment of 1p/19q status by fluorescence in situ hybridization assay: A comparative study in oligodendroglial, mixed oligoastrocytic and astrocytic tumors.
BACKGROUND
Due to overlapping histomorphological features, difference in clinical behavior and treatment response, establishing potential molecular markers to facilitate diagnosis of various genetic subtypes of diffuse gliomas is essential.


OBJECTIVE
To analyze 1p/19q status in diffuse gliomas and correlate it with epidermal growth factor receptor (EGFR) and p53 protein expression.


METHODS
1p/19q status in 43 cases was evaluated by fluorescence in situ hybridization assay. Glial fibrillary acidic protein (GFAP), EGFR and p53 were assessed by immunohistochemistry.


RESULTS
Glial fibrillary acidic protein immunopositivity was observed in oligodendrogliomas within minigemistocytes and gliofibrillary oligodendrocytes as perinuclear homogenous blobs. It also highlighted the intermingled reactive astrocytes. Astrocytomas and the astrocytic component of oligoastrocytomas showed a diffuse fibrillary type of staining. 1p and/or 19q loss was seen in 65% (13/20) of oligodendrogliomas and 66.6% (5/9) of mixed oligoastrocytomas. There was one case each of pediatric oligodendroglioma and mixed oligoastrocytoma, none of which showed 1p/19q loss. None of the astrocytomas including two pediatric cases showed this alteration (P < 0.05). p53 was expressed in 57.1% of astrocytomas (8/14), 33% of mixed oligoastrocytomas (3/9) and 10% of oligodendrogliomas (2/20). Majority of oligodendrogliomas (85%; 17/20) and oligodendroglial areas in mixed oligoastrocytomas (77.7%; 7/9) showed a membranous lace-like immunopositivity with EGFR. In contrast, all astrocytomas (Grade II and III) were EGFR negative.


CONCLUSIONS
Loss of 1p/19q is strongly associated with oligodendroglial phenotype, while astrocytic tumors are more likely to show p53 over-expression. p53 expression and 1p/19q status appear to be mutually exclusive.
Shukla
Bhaskar
B
Department of Pathology, All India Institute of Medical Sciences, New Delhi, India.
Agarwal
Shipra
S
Suri
Vaishali
V
Pathak
Pankaj
P
Sharma
Mehar Chand
MC
Gupta
Deepak
D
Sharma
Bhavani Shankar
BS
Suri
Ashish
A
Halder
Ashutosh
A
Sarkar
Chitra
C
D000293:Adolescent; D000328:Adult; D001254:Astrocytoma / Q000235:genetics* / Q000378:metabolism; D001932:Brain Neoplasms / Q000235:genetics* / Q000378:metabolism; D002888:Chromosomes, Human, Pair 19; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006801:Humans; D017404:In Situ Hybridization, Fluorescence / Q000379:methods*; D008297:Male; D008875:Middle Aged; D009837:Oligodendroglioma / Q000235:genetics* / Q000378:metabolism; D012189:Retrospective Studies; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D055815:Young Adult
D005904:Glial Fibrillary Acidic Protein; D016159:Tumor Suppressor Protein p53; C512478:EGFR protein, human; D066246:ErbB Receptors