Table 3.
The immunohistochemical and molecular studies including MMR genes, MMR protein, and MSI status in our cases.
| # | Diagnosis | Mutant MMR gene, variant allele frequency | MLH1/PMS2 | MSH2/MSH6 | MSI | 7p + &10q-/EGFR amplification/PTEN loss | BRAF mutation | TERT promoter mutation | ATRX/IDH1/K27M IHC | PD1/PDL1 | MGMT |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | GBM IDH-wildtype | MLH1, p.Ser685Phe, 36.1%, likely pathogenic | Loss/Loss | No loss/No loss | MSS | −/−/p | − | Present | +/−/− | −/− | M |
| 2 | GBM IDH-wildtype | MSH2, p.Leu372*, 94.7%, pathogenic | No loss/No loss | Loss/Lossa | MSI-H | −/−/p | − | − | +/−/− | −/− | UM |
| 3 | GBM IDH-wildtype, Lynch syndrome | MSH6, p.Ser602*, 48.6%, pathogenic | No loss/No loss | No loss/Loss | MSI-H | −/−/− | − | − | +/−/− | −/− | UM |
| 4 | GBM IDH-wildtype, Lynch syndrome | MSH2, p.Tyr405*, 92.9%, pathogenic | No loss/Loss | Loss/Lossa | MSI-H | −/−/− | − | − | +/−/− | −/− | M |
| 5 | GBM IDH-wildtype | MSH2, p.Gln510*, 16.3%, pathogenic | No loss/No loss | Loss/Lossa | MSI-L | −/−/p | − | Present | +/−/− | −/− | M |
| 6 | GBM IDH-wildtype | MSH2, splicing, 14.5%, pathogenic | No loss/No loss | Loss/Loss | MSS | −/−/− | − | Present | +/−/− |
A few (+) /weak (+) |
M |
| 7 | GBM IDH-wildtype | PMS2, p.Thr337fs, 57.02%, pathogenic | No loss/Loss | No loss/No loss | MSS | −/−/− | − | − | +/−/− | −/− | UM |
| 8 | GBM IDH-wildtype, Lynch syndrome | MSH6, p.Phe1088fs, 23.86%/p.Gln889fs, 44.46%, pathogenic | No loss/Loss | No loss/Loss | MSI-H | −/−/− | − | − | +/−/− |
A few (+) /weak (+) |
UM |
| 9 | Gliosaroma IDH-wildtype | MLH1, p.Arg127Ile, 5.0%, pathogenic | Loss/Loss | Lossa/No loss | MSS | −/−/− | − | − | +/−/− | −/weak (+) | M |
| 10 | DMG H3 K27M-altered | MLH1, p.Ala353fs, 54.3%, likely pathogenic | Loss/Loss | No loss/No loss | MSI-H | −/−/p | − | − | Loss/−/+ | −/− | UM |
| 11 | Astrocytoma, IDH-mutant, WHO grade 4 | MLH1, p.Arg687Trp, 87.1%, pathogenic | Loss/Lossa | No loss/No loss | MSI-H | −/−/− | − | − | Loss/+/− | −/− | M |
| 12 | Astrocytoma, IDH-mutant, WHO grade 4 | MSH6, p.Arg1172fs, 80.5%, pathogenic | No loss/No loss | No loss/Loss | ND | −/−/− | − | − | +/+/− | −/− | UM |
| 13 | Pleomorphic xanthoastrocytoma, Lynch syndrome | MSH6, p.Arg1334Gln, 55.06%, pathogenic | No loss/No loss | No loss/Loss | MSS | −/−/− | + (V600E) | − | +/−/− | −/− | M |
+ or p positive, − negative, Lossa Heterogeneous loss of expression, M MGMT promoter-methylated, UM MGMT promoter-unmethylated, MSS microsatellite stable, MSI-H microsatellite instability-high, MSI-L microsatellite instability-low, weak (+) weak positive (+/3) in 1% of tumor cells, A few (+) positive in up to 4/HPF, 7p+&10q- the concurrent gain of whole chromosome 7 and loss of whole chromosome 10, ND not done.