Abstract
Introduction In consonance with current the World Health Organization (WHO) classification of
the central nervous system (CNS) tumors (2016), histological diagnosis of gliomas
should be reinforced by molecular information. This study was performed to determine
the frequency of isocitrate dehydrogenase 1 (IDH1), α thalassemia/intellectual disability
syndrome X-linked (ATRX), p53, and BRAF V600E mutations in different grade astrocytomas
and oligodendrogliomas.
Methods Seventy-seven cases of astrocytoma and oligodendroglioma (7 pilocytic astrocytomas,
15 diffuse astrocytomas [DA], 4 anaplastic astrocytomas [AA], 29 glioblastomas [GBM],
and 22 oligodendrogliomas) were analyzed using immunohistochemistry for IDH1 mutant
protein, ATRX, p53, and BRAF as well as their clinicopathological features assessed.
Results All pilocytic astrocytoma and primary glioblastoma cases were negative for an IDH1 mutation. IDH1 mutation was detected in 66.7% (10/15) of DA, 50% (2/4) of AA, 20.7% (6/29) of glioblastomas,
and 81.8% (18/22) of oligodendroglioma cases. Loss of nuclear ATRX expression was
found in 86.7% (13/15), 75% (3/4), and 34.5% (10/29) of DA, AA, and GBM cases, respectively.
All oligodendroglioma cases showed retained ATRX expression. Both markers were found
statistically significant in the above tumors (p <0.05). BRAF V600E mutation was detected in a single case of pilocytic astrocytoma and pleomorphic xanthoastrocytoma
as well as both cases of epithelioid glioblastoma.
Conclusions IDH1 and ATRX mutations are very common in diffuse astrocytoma and anaplastic astrocytoma, while
they are rare in pilocytic astrocytoma and glioblastoma. Immunohistochemistry for
IDH1 and ATRX can successfully characterize the diffuse gliomas into molecularly defined groups
in the majority of the cases. BRAF V600E mutation is rare in astrocytic tumors in the Indian population.
Keywords
astrocytoma - oligodendroglioma - glioblastoma - isocitrate - dehydrogenase
