Epithelioid glioblastoma, light micrograph. Glioblastoma is a high-grade (WHO Grade IV) aggressive astrocytoma primarily seen in adults. Epithelioid subtype of glioblastoma consists of tumour cells with燼bundant eosinophilic cytoplasm, vesicular nuclei with prominent nucleoli, and distinct cytoplasmic borders. The cells are arranged in cohesive patternless sheets. It爎esembles metastatic carcinoma or melanoma爓hich must be ruled out.