Whether or not epithelioid glioblastomas are distinct from rhabdoid glioblastomas is at present unclear, however, the latter term should be avoided and is not recognised in the current WHO classification 2,3.
It is important to note that true epithelial differentiation of glioblastomas (typically squamous) is very rarely seen in adults but is distinct from epithelioid glioblastoma 2.
Unlike run-of-the-mill glioblastomas that are usually encountered in older adults, epithelioid glioblastomas have a predilection for young adults and children 1,3.
Epithelioid glioblastoma are WHO grade IV tumours 3. Interestingly, they sometimes co-exist with pleomorphic xanthoastrocytomas, however, their exact relationship is at present unclear 3.
These tumours are heterogeneous with large epithelioid cells that have abundant eosinophilic cytoplasm, vesicular chromatin, and prominent nucleoli. These cells are reminiscent of melanoma cells. Rhabdoid cells are also sometimes encountered 1.
Immunohistochemistry demonstrates a mixture of astrocytic and epithelial markers 3:
Epithelioid glioblastomas most frequently present as diencephalic or less frequently superficial cerebral hemispheric masses 1,2. Haemorrhage and leptomeningeal seeding are probably fairly common at the time of diagnosis 2.
These tumours are indistinguishable for glioblastoma on imaging, with enhancement, necrosis and diffusion restriction present in the vast majority of tumours 2.
Treatment and prognosis
Epithelioid glioblastomas are aggressive tumours with poor prognosis, even worse than ordinary glioblastomas 3. In one series the median survival was only 169 days 2.
These tumours also sometimes demonstrate systemic metastases, a very uncommon occurrence for other primary brain tumours 2.
In children the main differential is atypical teratoid / rhabdoid tumour (AT/RT), distinguished by universal lack of INI1 expression in AT/RT 2.
- 1. Louis DN, Perry A, Reifenberger G et-al. The 2016 World Health Organization Classification of Tumors of the Central Nervous System: a summary. Acta Neuropathol. 2016;131 (6): 803-20. doi:10.1007/s00401-016-1545-1 - Pubmed citation
- 2. Broniscer A, Tatevossian RG, Sabin ND et-al. Clinical, radiological, histological and molecular characteristics of paediatric epithelioid glioblastoma. Neuropathol. Appl. Neurobiol. 2014;40 (3): 327-36. doi:10.1111/nan.12093 - Free text at pubmed - Pubmed citation
- 3. Louis DN, Ohgaki H, Wiestler OD et-al. The 2007 WHO classification of tumours of the central nervous system. Acta Neuropathol. 2007;114 (2): 97-109. Acta Neuropathol. (full text) - doi:10.1007/s00401-007-0243-4 - Free text at pubmed - Pubmed citation
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