Introduction: Epithelioid Glioblastoma is a new provisional entity described as a variant of Glioblastoma, that has been added to the new classification of 2016. These are are seen in children and young adults and are associated with short survival. Here we are presenting seven cases of epithelioid glioblastoma.

Methods: All cases of glioblastoma were retrieved from the archives. The cases with histomorphological features of epithelioid glioblastoma were analysed. Immunohistochemistry for GFAP, ATRX, IDH , S100, EMA, CK, HMB-45 H3K27me3, and INI-1 was performed. EGFR amplification was assessed by FISH. BRAF V600E mutation, H3F3A K27 M and IDH 1 mutation were assessed by sequencing.

Results: Majority of Epitheliod GBMs ( 85%) occurred in young adults with slight female preponderance . The age of the patients ranged from 13 to 47 years. Duration of symptoms varied from 2 weeks to one month..All the cases were denovo .Radiologically all the cases were supratentorial, contrast enhancing with solid and cystic appearance..The histological hallmark of discohesive population of cells having eosinophilic cytoplasm with areas of confluent zonal necrosis was present in all the cases. Tumour giant cells were seen in 42% cases. Microvascular proliferation, existence of which is dubious was not seen in any of our case..Tumors were consistently positive for EMA,vimentin, variably positivie for GFAP, CK, S100 and negative for IDH 1INI 1, ATRX, H3K27me immunoexpression was retained. BRAF V600E mutations were seen in 29% cases. EGFR amplification, IDH 1/2 and H3F3A K27M mutations were seen in none.

Conclusions: Epithelioid morphology of a CNS tumor in a young adult or children with areas of necrosis should point diagnosis towards epithelioid glioblastoma, rather than metastasis.Though, BRAF V600E mutation is seen in half of these cases, there is no specific distinct and characteristic genetic alterations.

Patient Care: These tumors show early recurrence and leptomeningeal dissemination and tend to develop in younger patients compared to typical GBM. The prognosis is normally worse than typical GBM, even with intensive chemoradiotherapy after surgical resection. Thus, accurate diagnosis and effective therapy for epithelioid/rhabdoid GBM are required.

Learning Objectives: The strength of the study is that it highlights major clinical, radiological, histological and immunohistochemical characteristics of these rare tumors that can aid diagnosis. Epithelioid Glioblastomas are highly aggressive tumors having prognosis worse than conventional GBM. Hence, their identification holds an important prognostic value. It is associated with early progression and short survival despite of adjuvant therapies.

References: Mueller, W, Lass, U, Herms, J, et al. 2001Clonal analysis in glioblastoma with epithelial differentiationBrain Pathol 1139 -43. Sugimoto K, Ideguchi M, Kimura T, Kajiwara K, Imoto H, Sadahiro H, Ishii A, Kawano H, Ikeda E, Suzuki M. Epithelioid/rhabdoid glioblastoma: a highly aggressive subtype of glioblastoma.Brain Tumor Pathol. 2016 Apr;33(2):137-46.