Page 42 - Molecular features of low-grade developmental brain tumours

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CHAPTER 2
Materials and methods
SEGA tumour specimens
SEGA specimens were obtained from the following sites: the Academic Medical Center of Amsterdam, the University Medical Center Utrecht, University Medical Center Groningen, University Hospital Erlangen, University Hospital Münster, Medical University of Vienna, Children’s Memorial Health Institute in Warsaw, Meyer Children’s Hospital in Florence, Hacettepe University in Ankara, and the University Hospital de Santa Maria (CHLN) in Lisbon. Fifty-eight SEGAs and one SEN were available from 58 patients of which 56 met standard diagnostic criteria for TSC (Table 1) 33,34. Specimens were obtained and used in accordance with the Declaration of Helsinki and this study was approved by the Medical Ethics Committee of each institution.
Figure 1. Subependymal giant cell astrocytomas (SEGAs). A. Hematoxylin and eosin staining of a SEGA tumour presenting classical histological features, with giant cells (large cells with abundant eosinophilic cytoplasm and nuclei with prominent nucleoli; high magnification in insert) in a mixed glial background and blood vessels. B. GFAP showing areas of diffuse immunoreactivity. C. Variable expression of neuronal markers, including MAP2 is observed within the tumour (arrow shows MAP2 expression in a giant cell). D. HLA-DR shows prominent presence of microglial cells. E. CD3 staining shows intratumoural T lymphocytes (arrows). F. pS6 shows several positive tumour cells. Scale bars: 100 μm.
Histopathological evaluation
Tissue was fixed in 10% buffered formalin and embedded in paraffin. Paraffin-embedded tissue was sectioned at 6 μm, mounted on organosilane-coated slides (Sigma, St. Louis, MO, USA) and stained with hematoxylin-eosin (HE) for the morphological evaluation. Histological diagnosis was performed according to the 2016 WHO classification of the central nervous system 35. Sections of the most representative paraffin-embedded specimen of each case
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