Histo-Epidemiological Aspects and Preliminary Immunohistochemical Profile of Gliomas Diagnosed in Burkina Faso between 2014 and 2023

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Résumé

Introduction
Glial tumours are primary tumours of the central nervous system. They may be localised or diffuse. Diffuse gliomas are the most common primary tumours of the central nervous system encountered in neuro-oncological practice. The 5th edition (2021) of the WHO classification of tumours of the central nervous system requires that the morphological diagnosis be supplemented by the identification of molecular alterations using immunohistochemistry and molecular biology techniques. These techniques are still struggling to be implemented in resource-limited settings such as those in Burkina Faso. We initiated this study with the dual aim of establishing the histo-epidemiological profile of gliomas diagnosed in Burkina Faso between 2014 and 2023 according to the 2007 WHO classification, and of reporting the molecular alterations associated with diffuse gliomas using immunohistochemical techniques in line with modern criteria.
Methodology
We conducted a cross-sectional, descriptive and analytical study involving retrospective data collection, including all cases of histologically confirmed gliomas from all pathological anatomy laboratories in Burkina Faso between 1 January 2014 and 31 December 2023. For each case, we collated the available sociodemographic, clinical, radiological and pathological data. An immunohistochemical re-evaluation was then carried out on diffuse gliomas using formalin-fixed, paraffin-embedded (FFPE) tissue blocks. The panel of antibodies used included antibodies against: GFAP, IDH1-R132H, p53, ATRX, Olig2, INA and Ki-67.
Results
Over a ten-year period, we collected data on 463 CNS tumours, of which 154 were gliomas, representing 33.33%. The average annual incidence of gliomas was 15.4 new cases. The sex ratio was 1.75. The mean age of patients was 32.7 years, with a median of 30 years and a range of 1 to 80 years. Standard histological examination revealed 62.99% astrocytic tumours, 26.62% glioblastomas and 9.09% oligodendrogliomas.
Immunohistochemical analysis of 33 cases identified an IDH mutation in 78,8% of cases and yielded the following profiles :
-Seven low-grade astrocytomas (grade 2) with IDH mutation.
-Four anaplastic astrocytomas (grade 3) with an IDH mutation.
-Five gliomas without an IDH mutation (IDH wild-type), requiring further investigation.
-Five cases suggestive of oligodendroglioma (requiring confirmation by testing for 1p/19q co-deletion).
-Most notably, 12 cases initially classified as “IDH-mutated glioblastomas” were reclassified as “grade 4 IDH-mutated astrocytomas” according to the 2021 WHO classification.
Conclusion
This study, the first of its kind in Burkina Faso, confirms that gliomas affect a young population there, with a clear predominance of male patients. Above all, it highlights the very high prevalence of IDH-mutated gliomas (nearly three-quarters of the cases analysed). This molecular profile has direct implications for prognosis and treatment options. However, it should be interpreted with caution as it is based on a sample of only 33 cases and cannot be generalised at this stage of the study. Furthermore, twelve (12) gliomas were reclassified using the 2021 WHO criteria. This clearly illustrates the role of immunohistochemistry, even in a resource-limited setting, in refining the diagnosis and better guiding patient management.

Mots-clés

Gliomas, Immunohistochemistry, IDH Mutation, WHO 2021 Classification, Epidemiology, Burkina Faso