Diagnostic algorithm for pathological evaluation of gliomas in a resource-constrained setting.Introduction
 Gliomas are the most common primary intracranial tumors.  The current World Health Organization (WHO) classification of central nervous system tumors recommends integrated histo-molecular diagnosis of gliomas.  However, molecular testing is not available in even most of the advanced centers of our country, and histopathology aided with immunohistochemistry (IHC) is still widely used for diagnosis.  Immunohistochemical markers such as iso-citrate dehydrogenase1 (IDH1) and Alpha Thalassemia/Mental Retardation Syndrome X-linked (ATRX) can be reliably used for the correct diagnosis, prognosis, and treatment of gliomas.


 We aimed to develop a diagnostic algorithm by integrating morphology, IDH1, and ATRX status of gliomas seen in our institute for 1 year.


 Analytical cross-sectional study.


 This study included 60 histopathologically confirmed cases of astrocytic (n = 51) and oligodendroglial tumors (n = 9).  Clinical, radiological, and histopathological features were noted and tumor grades assigned according to the WHO recommendations.  IDH1 and ATRX mutation status was evaluated using IHC.  The tumors were divided into three molecular groups on the basis of their IDH1 and ATRX mutation status: (1) Group 1: IDH1 negative and ATRX positive, (2) Group 2: IDH1 positive and ATRX positive, (3) Group 3: IDH1 positive and ATRX negative.


 Seizures, headache, and hemiparesis were the most common modes of presentation.  The tumor subtypes studied were glioblastoma (n = 32), anaplastic astrocytoma (n = 7), diffuse astrocytoma (n = 6), oligodendroglioma (n = 6), pilocytic astrocytoma (n = 6), and anaplastic oligodendroglioma (n = 3).  IDH1 mutation was present in 26 cases including anaplastic astrocytoma (n = 7), diffuse astrocytoma (n = 6), oligodendroglioma (n = 5), secondary glioblastoma (n = 5), and anaplastic oligodendroglioma (n = 3).  , loss of ATRX was observed in 17 cases including diffuse astrocytoma (n = 5), anaplastic astocytoma (n = 5), anaplastic oligodendroglioma (n = 3), oligodendroglioma (n = 3), and secondary glioblastoma (n = 1).  All six cases of pilocytic astrocytoma were negative for IDH1 and ATRX mutation.  There were 34 patients in Group 1 (IDH1- and ATRX +), nine cases in Group 2 (IDH1 + and ATRX +), and 17 patients in Group 3 (IDH1 + and ATRX-).


 Conclusion
 Diagnosis of gliomas should be based on a detailed clinicoradiological and histopathological assessment, followed by genotypic characterization.  Evaluation for IDH1and ATRX status has both diagnostic and prognostic value as it helps in differentiating gliomas from reactive gliosis, primary glioblastoma from secondary glioblastoma, and pilocytic astrocytoma (WHO grade I) from diffuse astrocytoma (WHO grade II).  Tumors with IDH1 mutations have a better outcome than those with wild-type IDH.  IHC can serve as a useful surrogate to conventional molecular tests in resource-constrained settings.  By devising an algorithm based on morphological and IHC features, we were able to stratify gliomas into three prognostic subgroups.
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