PMC6336597_01
Neuroradiological features. A frontoparietal tumor exhibiting a neuroradiological cyst with mural nodule pattern on magnetic resonance imaging. The mural nodule is hypointense in the T1-weighted (A) and hyperintense in the T2-weighted (B) images. T1-weighted gadolinium-enhanced image reveals the brain tumor as a heterogeneously enhancing mural nodule with a rim-enhancing cyst (C).
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F1
T1- and T2-weighted images, respectively. The mass appeared as a heterogeneously enhanced mural nodule with a rim-enhancing cyst (diameter, 45 mm) on the T1-weighted gadolinium-enhanced images (Fig. 1A-C).
Histopathological features. Histopathologically, the highly cellular tumor exhibits pseudopapillary structures with non-hyalinized central capillaries (A and B; hematoxylin and eosin [H&E], magnification x40 [A] and x100 [B]). Non-hyalinized vascular cores (vc) surrounded by both fibrillary (fib) and mini-gemistocytic (gem) neoplastic cells; these pseudopapillary structures are covered by naked neoplastic cells (nkd) (C; H&E, magnification x400). Focal microvascular proliferation is also observed (D; H&E, magnification x200).
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F2
Histopathologically, the tumor was a hypercellular neoplasm characterized by the formation of pseudopapillary structures with non-hyalinized capillaries (Fig. 2A and B), and infiltrated the cerebral parenchyma. The papillary structures, which were surrounded by naked neoplastic cells, comprised fibrillary and mini-gemistocytic neoplastic cells that tended to proliferate around the non-hyalinized capillaries (Fig. 2C). Focal microvascular proliferation was observed in the tumor specimen (Fig. 2D) and lacked necrosis.
Immunohistochemical features. Immunohistochemically, neoplastic cells express glial fibrillary acidic protein (A; magnification x200), and oligodendrocyte transcription factor 2 (B; magnification x200). Tumor stroma reveals immunoreactivity against synaptophysin (C; magnification x200). A few residual neurons in the tumor show neuronal nuclei (NeuN) immunopositivity (D; x200), and neurofilament immunoreactivity is focally observed in the tumor stroma (E; magnification x200). The tumor exhibits no immunoreactivity against mutant isocitrate dehydrogenase (IDH1) R132H (F; magnification x200) and retains nuclear expression of alpha-thalassemia/mental retardation syndrome X-linked (G; magnification x200) and INI-1 (H; magnification x200). Additionally, MIB-1 labeling index is very high (63.4%) (I; magnification x100).
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F3
Immunohistochemically, the neoplastic cells were positive for S-100 protein, glial fibrillary acidic protein (Fig. 3A), and oligodendrocyte transcription factor 2 (Olig2) (Fig. 3B). However, synaptophysin (Fig. 3C), NeuN (Fig. 3D), and NFP (Fig. 3E) immunoreactivities were observed in both non-neoplastic residual neuronal cells and neuropil. ATRX (Fig. 3G) protein and integrase interactor 1(INI1) protein (Fig. 3H). Additionally, the MIB-1 labeling index was 63.4% (Fig. 3I).
Fluorescence in situ hybridization (FISH) for detecting 1p/19q co-deletion. FISH analysis for chromosomes 1p and 19q reveals co-deletion of 1p36 and 19q13 (A; red dot, 1p36 signal; green dot, 1q25 signal) (B; red dot, 19q13 signal; green dot, 19p13 signal).
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F4
Fluorescence in situ hybridization analysis of chromosomes 1p and 19q revealed deletion of 1p36 and 19q13, respectively (Fig. 4A and B).