PMC9119689_01
(a) Preoperative computed tomography (CT) scan showing a low-density area containing a focal calcified hyperdense lesion in the left cerebellar hemisphere (arrows). (b-d) Preoperative magnetic resonance imaging (MRI) scan showing multiple lesions in the left cerebellar hemisphere and vermis (arrowheads). (b) T1-weighted image showing hypointensity. (c) T2-weighted and (d) fluid-attenuated inversion recovery (FLAIR) image showing hyperintensity. Notably, there is no peri-tumoral edema or space-occupying effect.
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Computed tomography (CT) showed a low-density area and calcification of the left cerebellar hemisphere (Fig. 1a). Magnetic resonance imaging (MRI) also showed multiple lesions of the left cerebellar hemisphere and vermis (Fig. 1b-d); the lesions appeared as hypointensities on T1-weighted images and hyperintensities on T2-weighted images. Sanger sequencing revealed no mutations in in IDH-1, IDH-2, BRAF and TERT genes (Supplementary Fig. 1a-d). Multiplex ligation-dependent probe amplification (MLPA) analysis revealed that neither IDH mutation nor 1p19q codeletion had been detected in the lesion (Supplementary Fig. 1e).
Intraoperative photograph during resection of the left cerebellar tumor. (a) The lesion (arrow) was gray and well circumscribed. (b) The lesion was observed with slight fluorescence induced by 5-aminolevulinic acid (5-ALA). (c) Partial resection was performed.
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The boundary was well defined but could not detached from the cerebellar hemisphere (Fig. 2a). This lesion showed barely visible 5-aminolevulinic acid (5-ALA) fluorescence (Fig. 2b). Several pieces of the left cerebellar hemisphere were removed for biopsy (Fig. 2c).
(a) Photomicrography of the lesion shows oligodendrocyte-like cells (OLCs) and specific neuroglial elements distributed over a wide range (hematoxylin-eosin stain [H&E], x40). (b) Floating neurons are observed in the myxoid interstitial tissue (H&E, x100). (c) Neurons at various stages of differentiation are observed with round nuclei, defined nucleoli, and eosinophilic reticulum intermixed with OLCs (H&E, x200). (d) Olig2-positive cells (x200). (e) Chromogranin A-positive cells (x200). (f) Glial fibrillary acidic protein (GFAP) -positive cell processes are densely observed throughout the lesion (x200).
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A histological examination of the lesion showed oligodendrocyte-like cells (OLCs), with round medium-sized nuclei that were distributed over a wide range (Fig. 3a). The background was edematous, with a viscous consistency, and small myxoid cystic lesions including differentiated neurons, which corresponded to "floating neuron," were observed (Fig. 3b). Neurons in various stages of differentiation with round nuclei, defined nucleoli, and eosinophilic reticulum were intermixed with OLCs (Fig. 3c). On immunohistochemistry, olig2 labeling indicated the presence of OLCs (Fig. 3d). Chromogranin A (Fig. 3e) and neuronal nuclei (NeuN) labeling indicated differentiated neurons. Glial fibrillary acidic protein (GFAP)-positive cell processes were densely observed throughout the lesion (Fig. 3f).