PMC6018091_01
Histology and immunohistochemistry. Hematoxylin-eosin stained image from a representative area of the tumor shows a small to medium sized primitive cellular population. A desmoplastic micronodular architecture is revealed by reticulin staining. The tumor cells are positive with synaptophysin and weakly with GFAP. INI-1 expression is preserved. The proliferative index (MIB-1) reaches 70%.
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F1
Histopathological analysis including reticulin staining revealed a desmoplastic/nodular MB (confirmed by a central review by T.P.) as shown in Figure 1. Of note, nuclear INI-1 staining was preserved (Figure 1) while P53 immunostaining showed nuclear positivity only in a small proportion of the tumor cells (data not shown).
Subgroup-specific immunohistochemical markers. The tumor cells show only cytoplasmic but no nuclear beta-catenin positivity, and are stained with antibodies against filamin A, Gab1 and Yap1. These characteristics are consistent with SHH MB.
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F2
Complementary immunophenotypic characterization as described suggested a MB with SHH activation, TP53 wild-type (Figure 2).
Copy number profile. Array data showed a low density copy number profile which indicates an almost flat genome without relevant chromosomal aberration.
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F3
Calculation of a low density copy number profile from the array data indicated a flat genome without relevant chromosomal aberration (Figure 3).
Assessment of overall CpG methylation and CpG island methylation levels. (Left) The distribution of mean beta-values for all CpG-probes of the EPIC methylation array is displayed as box-plots for IDH mutant astrocytoma, IDH mutant oligodendroglioma, medulloblastoma SHH A (children and adult), medulloblastoma SHH B (infant) and the presented case. IDH mutant astrocytoma and oligodendroglioma are given for comparison because of the known CpG Island Methylator Phenotype (CIMP) associated with IDH mutations in these tumors. The overall CpG methylation of our presented cases was not higher than that in other medulloblastoma groups and lower than that in the CIMP tumors. (Middle) When just the CpG island associated CpG sites were analyzed, the mean beta value of our case was clearly higher than that of other medulloblastoma of the same age group and was well in the range of the other CIMP tumors indicating some degree of CpG island hypermethylation. (Right) Density plot analysis of the distribution of beta-values ("methylation ratio") of all CpG probes also indicated a moderate relative hypermethylation.
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F4
Assessment of overall CpG methylation and CpG island methylation levels of the tumor showed relative CpG hypermethylation compared to other reference classes of MB (Figure 4).