Table 1 Comparison of imaging features, histopathologic appearance, molecular data, therapy regimens and clinical course of the three presented cases of IHG harboring a TRIM24::MET fusion

Imaging features

Disseminated tumors with CE in lateral ventricles and cerebellopontine angle, diffuse LME

Diffusion restricted tumor with CE in the left frontal lobe and lateral ventricle, internal calcifications, no LME

Heterogeneous well-circumscribed tumor with CE in left parietal, occipital and temporal lobe, diffuse LME

Histopathology

Papillary neuroepithelial tumor, moderate cell density. MIB1-LI 5%. GFAP and MAP2 positive, classified as LGG

Well circumscribed glial tumor, calcifications, GFAP and Olig2 positive, MIB1-LI 10%, classified as HGG

Homogeneous glial tumor, high cell density, GFAP and Olig2 positive, MIB-1 LI > 25%, classified as LGG

DNA methylation profile (v18.2)

No significant conformity, highest classifier score: IHG (0.54)

n.a

No significant conformity, cluster in proximity to IHG on t-SNE brain tumor world map

Molecular profile

TRIM24::MET fusion, homozygous CDK2NA deletion

TRIM24::MET fusion

TRIM24::MET fusion, homozygous CDK2NA deletion

Extent of surgery

Biopsy only

Incomplete resection (IR), secondary IR after progression

Biopsy followed by IR, secondary IR after progression

Adjuvant therapy

VBL weekly for 18 months

Induction: VCR, CB, IFO and VP-16. MT: VCR, VP-16, CB and CPM (CCG-9921)

After progression: CCNU/TMZ

Induction: HD-MTX, VCR, CP and CPM. MT: CPM (SJYC07)

After progression: carbozantinib

Outcome

Treatment response,

minor tumor residuals, Progression-free 3 years after diagnosis

PD 2 years after first-line treatment, progression-free 5 years after 2nd resection

PD 6 months after initial therapy, PD 3 months after 2nd treatment, died 17 months after diagnosis