PMC6011152_01
Transversal 1.5 Tesla FLAIR images (a) of a left cerebellar and vermal medulloblastoma show poor tumor delineation and inhomogeneous hyperintensity. Medulloblastomas normally appear hypointense relative to gray matter on T1w images with minimal to patchy contrast enhancement (b) and moderate restriction on diffusion weighted images (c).
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fig1
Cranial MRI revealed a low and focal contrast-enhancing nodular tumor in the left cerebellar hemisphere and upper vermis (Figure 1).
A small, round, blue cell, neuroectodermal tumor ((a), HE) showing a nodular architecture and a dense reticulin fiber network ((b), Gomori). Tumor cells showed nuclear expression of YAP1 (c) and cytoplasmic expression of GAB1 (d) while there was no nuclear expression of beta-catenin (e). Ki67-labelling reveals high proliferative activity (f).
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fig2
There was no MYC- or MYCN-amplification detectable (Figure 2).
PMC6011152_02
Transversal T1w image at 1.5 Tesla (a) shows a large hypointense tumor of the right cerebellar hemisphere with a hyperintense cyst on FLAIR images (b), which fills most of the fourth ventricle and causes obstructive hydrocephalus (not shown). Susceptibility weighted images (c) reveal hemosiderin deposits in the caudal tumor parts. Because of its dense cellularity, this tumor shows moderate restriction on diffusion weighted images (d).
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fig3
The tumor caused occlusive hydrocephalus but no surrounding edema (Figure 3).
A small, round, blue cell, neuroectodermal tumor ((a), HE) without nodular architecture and without reticulin fiber network ((b), Gomori). Tumor cells showed expression of synaptophysin (c) but no expression of YAP1 and GAB1 (d). There was no nuclear expression of beta-catenin (e). Ki67-labelling reveals high proliferative activity (f).
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fig4
The diagnosis was that of a classical MB (WHO grade IV) (Figure 4).