Glioblastoma with true epithelial differentiation; a rare variant

Abstract

Aims A case report presentation with associated literature review to discuss a rare variant of glioblastoma that can cause diagnostic confusion with epithelial metastases to the brain. Methods Photographic and descriptive presentation of a case received by the Department of Anatomical Pathology (SA Pathology) at Flinders Medical Centre, South Australia. A subsequent literature review of ‘glioblastoma with epithelial differentiation’ was undertaken through electronic database searches of PubMed, MEDLINE and Google Scholar. Results On light microscopy, this brain tumour showed classic morphological areas of a glioblastoma (WHO grade IV) as well as infiltrating cohesive clusters of malignant epithelioid cells. The epithelioid clusters showed a trabecular architecture with no evidence of glandular or squamous differentiation. Immunohisto-chemistry confirmed GFAP positivity in the classic glioblastoma areas and cytokeratin positivity in the epithelial areas. The patient had no relevant clinical history and radiological investigations failed to detect any other mass lesions. A diagnosis of glioblastoma with true epithelial differentiation was made. Discussion Glioblastoma with true epithelial differentiation is a rare variant that is not currently described in the WHO Classification of Tumours of the Central Nervous System. Its presentation may cause diagnostic confusion, mimicking metastatic carcinoma or raising the suspicion of a collision tumour.