Astroblastoma: beside being a tumor entity, an occasional phenotype of astrocytic gliomas?

Abstract

Marta Mellai,1 Angela Piazzi,1 Cristina Casalone,2 Silvia Grifoni,2 Antonio Melcarne,3 Laura Annovazzi,1 Paola Cassoni,4 Tetyana Denysenko,1 Maria Consuelo Valentini,5 Angelina Cistaro,6,7 Davide Schiffer1 1Neuro-Bio-Oncology Center, Policlinico di Monza Foundation/Consorzio di Neuroscienze, University of Pavia, Vercelli, Italy; 2Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d'Aosta, Turin, Italy; 3Department of Neurosurgery, CTO Hospital/Città della Salute e della Scienza, Turin, Italy; 4Department of Medical Sciences, University of Turin, Turin, Italy; 5Department of Neuroradiology, CTO Hospital/Città della Salute e della Scienza, Turin, Italy; 6Positron Emission Tomography Center IRMET S.p.A, Euromedic Inc., Turin, Italy; 7Institute of Cognitive Sciences and Technologies, National Research Council, Rome, Italy Abstract: The diagnosis of astroblastoma is based on a typical histological aspect with perivascular distribution of cells sending cytoplasmic extensions to the vessels and vascular hyalinization. These criteria are useful for standardizing the identification of the tumor, but, in spite of this, there are discrepancies in the literature concerning the age distribution and the benign or malignant nature of the tumor. Three cases are discussed in this study: Case 1 was a typical high-grade astroblastoma; Case 2 was an oligodendroglioma at the first intervention and an oligoastrocytoma at the second intervention with typical perivascular arrangements in the astrocytic component; Case 3 was a gemistocytic glioma with malignant features and typical perivascular arrangements. Genetic analysis showed genetic alterations that are typical of gliomas of all malignancy grades. Using the neurosphere assay, neurospheres and adherent cells were found to have developed in Case 1, while adherent cells only developed in Case 2, in line with the stemness potential of the tumors. The cases are discussed in relation to their diagnostic assessment as astroblastoma, and it is hypothesized that the typical perivascular distribution of cells may not indicate a separate and unique tumor entity, but may be a peculiarity that can be acquired by astrocytic gliomas when an unknown cause from the tumor microenvironment influences the relationship between vessels and tumor cells. Keywords: gliomas, cell lines, histology, genetics