Abstract
Some glioblastoma can lack robust evidence of classic glioma markers like OLIG2 or GFAP. Such tumors seem to frequently be poorly differentiated morphology and are often referred to as glioblastoma with PNET like area or “dedifferentiated” GBM in common practice and may not be identified as gliomas or GBM at all. The incidence and clinical features of “dedifferentiated” GBM is not known. Therefore, we undertook this retrospective study to evaluate a large series of patients with glioblastomas at Brigham and Women’s hospital and Dana-Farber Cancer Institute from 2010-2014. The goal of this study was to estimate the incidence of dedifferentiated glioblastomas and to examine their genomic profile and the clinical characterization. A total of 23 patients out of the 733 patients (3.13%) were identified to have the “dedifferentiated” phenotypes. have examined the clinical, histological, staining patterns, and the genomic print of a cohort of challenging cases of “dedifferentiated” glioblastomas. Our study shows considerable heterogeneity at the molecular level. This phenotype can be a diagnostic challenge for the pathologists because of its rarity and lack of the expression of classic glial immunohistochemical markers, we found that these glioblastoma lacked OLIG2 expression and variable histological features. They have more aggressive clinical course with tendency to leptomeningial spread. Recognizing this phenotype is important for patient’s managements.