Multimodal magnetic resonance imaging (MRI) of juvenile and adult diffuse hemispheric gliomas with H3 G34-mutation: a case description

Introduction

H3F3A was reported to encode the replication-independent histone 3 variant H3.3, and G34R mutation could lead to amino acid substitutions (GGG → AGG, glycine → arginine) (1). This mutation always occurs in young adults and teenagers and has an adverse effect on prognosis (2). A previous study has revealed that H3.3 G34 mutations are rare (less than 1%) in patients with primary gliomas (3). A H3 G34R mutation has become an important molecular feature for defining a new tumour subgroup, diffuse hemispheric glioma, H3 G34-mutant (4). A previous study revealed that, histopathologically, G34R-mutant tumours in the brain can be classified as either glioblastomas (GBMs) or anaplastic pleomorphic xanthoastrocytomas (PXAs) (5). At present, only a few studies have revealed the imaging features of G34R-mutant tumours, revealing that these tumours exhibit slight or no contrast enhancement (3,6). Few studies have outlined the imaging features of this rare mutation in gliomas, and even fewer reports have revealed the multimodal magnetic resonance (MR) imaging features in adolescent and adult patients. We present two cases of diffuse hemispheric gliomas with H3 G34 mutation (DHG-G34m), classified as World Health Organization (WHO) grade 3 and 4 tumours in a pediatric patient and an adult patient, respectively (4,7). Our report includes details of both conventional and functional MR imaging features and provides information on treatment and follow-up.

Case presentation

All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). This study was approved by the Institutional Review Board (IRB) of West China Hospital of Sichuan University (No. 745 of 2023). Written informed consent was obtained from the patient or the patient’s parents for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Two patients were recruited for our study: a 13-year-old girl and a 26-year-old woman. In both patients, multimodal magnetic resonance imaging (MRI) of the brain revealed a solid lesion. Approximately 1 or 2 weeks later, both patients underwent surgical resection or biopsy. Histopathological and pyrosequencing-based analysis of the removed lesions revealed that both patients had high-grade gliomas with H3F3A G34R mutation. After partial resection, one patient underwent radiation therapy with adjuvant chemotherapy with temozolomide in our hospital, and the other patient underwent subsequent treatment at another hospital. Patients were recruited in 2020 at the Department of Neurosurgery.

Two patients underwent brain MR examinations on the same 3T clinical scanner with a 20-channel phased array head coil (Skyra, Siemens Healthcare, Erlangen, Germany). The main protocols and parameters were as follows: (I) conventional MR imaging included fast spin-echo T2-weighted imaging with fat-suppression (repetition time/echo time, TR/TE =4,500/105 ms), axial T2 fluid-attenuated inversion recovery (FLAIR, TR/TE =6,000/81 ms, 5-mm slice thickness) and three-dimensional (3D) T1-weighted magnetization-prepared rapid acquisition gradient echo (T1_MPRAGE) (176 sagittal sections, TR/TE =1,630/2.3 ms, flip angle =8°, 1 mm slice thickness, and matrix =256×232); (II) functional MR imaging included diffusion-weighted imaging (DWI) (42 axial sections, TR/TE=5,300/102 ms, 5 mm slice thickness, matrix =192×192, diffusion-weighted directions was 30 (b=0 and 1,000 sec/mm²); diffusion-tensor imaging (DTI) (62 axial sections, TR/TE =6,000/93 ms, 3 mm slice thickness, matrix =128×128, b=0 and 1,000 sec/mm²) and perfusion-weighted imaging (PWI) (acquired after a bolus injection of gadolinium-based contrast agent (5 mL/s, 0.1 mmol/kg body weight), with 60 phase images and 1,260 axial sections, TR/TE =1,640/30 ms, flip angle = 90°, 5 mm slice thickness, matrix =128×128, field of view (FOV) =22 cm × 22 cm, followed by post-contrast T1_MPRAGE); (III) metabolic MR imaging was performed using multi-voxel ¹H-magnetic resonance spectroscopy (MRS) (3 mm slice thickness, TR/TE =1,700/135 ms, number of excitations (NEX) =1, FOV =16 cm × 16 cm, volume of interest =8 cm × 8 cm, each voxel size =1 cm × 1 cm × 0.3 cm).

Case 1

A 13-year-old girl with DHG-G34m presented with progressive weakness in the left limb that persisted for more than 20 days, resulting in an inability to walk at the time of admission. Upon neurological examination, only the left limb showed decreased muscular strength, rated as Grade 3. There were no significant abnormalities observed in higher cortical functions or in deep or superficial sensory functions. Furthermore, there were no signs indicating the involvement of the pyramidal tract.

T2WI on MRI revealed a lesion with diffuse high signal intensity in the right frontal, insular and temporal lobes (Figure 1). The lesion produced a remarkable mass effect, and the midline structure of the brain appeared slightly deviated to the left side. The apparent diffusion coefficient (ADC) value was lower than that of the contralateral normal brain. In addition, DTI revealed significant regional disruption of the brain fibre bundles. A high cerebral blood volume (CBV) and increased Cho/NAA values indicate the malignancy of the lesion. However, only a small part of the lesion was enhanced on post-contrast T1WI. According to the MRI features, which include obscure boundaries, heterogeneous enhancement, necrosis, haemorrhage, diffusion restriction, an inverted choline/N-acetylaspartate (Cho/NAA) ratio and high perfusion, we initially diagnosed the tumour as a glioma, especially high-grade diffuse glioma. The differential diagnosis based on MRI­ should include ependymoma, pilocytic astrocytoma and embryogenic tumours, such as medulloblastoma and atypical teratoid/rhabdoid tumours.

Figure 1 Multimodal MR image of the patient in case 1, a 13-year-old girl. Preoperative MR imaging revealed a mass in the right frontal, insular and temporal lobes. Axial structural MR imaging revealed heterogeneous hypointensity on T1WI (A) and hyperintensity on T2WI (B), and nodular short T1 and short T2 signals were observed inside the tumour. This finding suggested possible necrosis and haemorrhage within the tumour and was confirmed on axial SWI (F). The FLAIR images revealed a solid lesion with a significant mass effect and mild oedema, which led to the midline structure of the brain shifting slightly to the left side (C). DTI showed significant disorder and disruption of the white matter fibre bundles and that the fibre bundles in the internal capsule area were squeezed inwards. Moreover, significant heterogeneous patchy contrast enhancement (G) was found within the lesion, especially in the area adjacent to the bleeding focus. The ADC map revealed partially restricted diffusion of the tumour entity (H). The NAA/Cho ratio was inverted on the MRS image (I), and a high CBV of the lesion is shown on the perfusion images (E). Ins, inositol; Cho, choline; Cr, creatine; Glx, glutamate and glutamine; NAA, N-acetylaspartate; MR, magnetic resonance; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging; SWI, susceptibility weighted imaging; FLAIR, fluid attenuated inversion recovery; DTI, diffusion-tensor imaging; ADC, apparent diffusion coefficient; NAA/Cho, N-acetylaspartate/choline; MRS, magnetic resonance spectroscopy; CBV, cerebral blood volume.

After 2 weeks, she underwent maximal safe resection and cerebral decompression at our hospital. Postoperative immunostaining revealed p53 (+), GFAP (+), IDH1 (−) and ATRX (−), and the anti-Ki67-labelled proliferation index was 70% (Figure 2). This lesion was classified as a GBM (WHO grade 4, high grade). In addition, H3F3A G34R mutation and O-6-methylguanine-DNA methyltransferase (MGMT) promoter methylation were detected, but telomerase reverse transcriptase (TERT) promoter mutation was not detected. Postoperatively, the patient occasionally experienced headache and vomiting as well as a decrease in left limb muscle strength. Six days later, the patient requested to be referred to another hospital for further treatment. The aforementioned symptoms were alleviated at the time of discharge. She was treated with concurrent chemoradiotherapy (radiation therapy plus temozolomide, RT plus TMZ), followed by TMZ in that hospital. By the 2-month follow-up examination, her limb motor function had improved.

Figure 2 Pathological findings of the patient in case 1. H&E, original magnification 200× (A) and 400× (B); the tumour cells were immunohistochemically negative for ATRX and oligo2 (C,F; 100×) and positive for GFAP and p53 (D,G; 100×); (E) the proliferation index of anti-Ki67-labelled (MIB1, Dako) cells was 70% (100×); and the H3F3A G34R mutation was identified through pyrosequencing-based analysis [(H,I) H3A-MHK64; HIS-MHK64]. H&E, hematoxylin and eosin; ATRX, α thalassemia/mental retardation syndrome X-linked; GFAP, glial fibrillary acidic protein.

Case 2

A 26-year-old woman with DHG-G34m presented with a 2-month history of weakness and numbness in the right upper and lower limbs. Over the course of a month, her symptoms progressively worsened, and she began to drool from the right corner of her mouth. During the 20 days thereafter, her condition deteriorated further, leading to progressive weakening of her right distal limbs, changes in the superficial sensory function on her right side, a hemiplegic gait, and signs indicating the involvement of the pyramidal tract. Consequently, she sought medical attention at the Emergency Department of our hospital.

Multimodal MR imaging examination (Figure 3) revealed hyperintense lesions in the left basal ganglia and bilateral centrum semiovale on T2WI and FLAIR images, with no evident postcontrast enhancement. DWI revealed mildly restricted diffusion, and PWI revealed slightly increased CBV. DTI showed local destruction of brain fibres. MRS revealed a significant increase in the Cho/NAA ratio, which indicated a high likelihood of neoplastic lesions. Initially, based on MRI findings, the tumour was diagnosed as a diffuse glioma. However, the possibility of inflammatory lesions or early-stage lymphoma could not be entirely ruled out.

Figure 3 Multimodal MR imaging of a 26-year-old woman with DHG-G34m. Preoperative MR imaging revealed bilateral lesions with slightly low signal intensity on T1WI (A) and high signal intensity on T2WI (B) in the bilateral centrum semiovale. The FLAIR image revealed a hyperintense tumour with an obscure boundary (C). DTI showed slight destruction of the fibres (D), and the CBV (E) images showed a slightly increased value. In addition, there was no haemorrhage on SWI (F) and almost no contrast enhancement on postcontrast T1WI (G); however, there was mildly restricted diffusion on the ADC map (H). MRS revealed an obvious inverted NAA/Cho ratio (I). Ins, inositol; Cho, choline; Cr, creatine; Glx, glutamate and glutamine; NAA, N-acetylaspartate; MR, magnetic resonance; DHG-G34m, diffuse hemispheric gliomas with H3 G34 mutation; T1WI, T1-weighted imaging; T2WI, T2-weighted imaging; FLAIR, fluid attenuated inversion recovery; DTI, diffusion-tensor imaging; CBV, cerebral blood volume; SWI, susceptibility weighted imaging; ADC, apparent diffusion coefficient; MRS, magnetic resonance spectroscopy; NAA/Cho, N-acetylaspartate/choline.

The patient had a normal cerebrospinal biochemistry. Corticoids (prednisone, 20 milligrams once a day) were used to treat symptoms, and the patient’s symptoms were not relieved. After multidisciplinary treatment and providing informed consent, she underwent a stereotactic biopsy (STB) one week later. According to the results of the histological analysis, the sample was classified as a WHO grade 3 astrocytoma (lower-grade glioma). Immunostaining revealed diffuse positivity for GFAP and p53, and the anti-Ki-67-labelled proliferation index was 10%. ATRX was negative, and no IDH1 mutation was identified. In addition, pyrosequencing-based analysis revealed a H3.3 G34R mutation (Figure 4). Moreover, MGMT promoter methylation was detected, but TERT promoter mutation was not detected. On the second day after surgery, the patient occasionally experienced headaches, which subsided on the third day after surgery. Radiation therapy was subsequently performed at our hospital. After the standard RT, she received chemoradiation with concurrent and adjuvant TMZ for approximately 1 month, followed by treatment with only TMZ for approximately 2 months. By the 5-month follow-up visit, her limb motor function had improved.

Figure 4 Pathological findings of the patient in case 2. H&E, original magnifications 200× (A) and 400× (B); the tumour cells were immunohistochemically negative for ATRX (C; 100×) and positive for oligo2 (F; 100×), GFAP (D; 100×) and p53 (G; 100×); (E) the proliferation index of anti-Ki67-labelled (MIB1, Dako) cells was 10% (100×); the H3F3A G34R mutation in tumour cells (H: H3AMHK44; I: HIS-MHK44) was identified through pyrosequencing-based analysis. H&E, hematoxylin and eosin; ATRX, α thalassemia/mental retardation syndrome X-linked; GFAP, glial fibrillary acidic protein.

Discussion

We report two histopatholigcally diagnosed cases of DHG-G34m, including one WHO grade 4 (high grade) GBM in a girl, and one WHO grade 4 glioma in a woman. Based on the histopathological results, both patients were ATRX (−), IDH1 (−), p53 (+), GFAP (+), and had high anti-Ki67-labelled proliferation indices (up to 10% or more). These genetic signatures were consistent with those of previous studies, such as ATRX loss (8), high enrichment of TP53 mutation (9) and IDH-wildtype (10). ATRX loss is considered to have value for predicting the prognosis of astrocytic tumours (8). Moreover, radiographic characteristics on functional MR images in both cases indicated high-grade gliomas, such as high perfusion manifestations (on CBV images) and increased Cho/NAA values on the MRS images.

Two cases of diffuse hemispheric gliomas, both featuring H3.3 G34R mutations, were reported in this study.

The tumours were located in the cerebral hemisphere, and both hemispheres were involved in the young patient (WHO grade 4). This finding is consistent with previous research that revealed that H3.3 G34R-mutant gliomas often affect both hemispheres. Furthermore, the pathological diagnosis was invariably GBM multiforme in the young patient (3,10,11).

The multimodal MR images of the two patients revealed high-perfusion tumours with notable increases in the Cho/NAA values. However, the MR images of the older patient (case 2) showed diffuse lesions in the bilateral cerebral hemisphere proximal to the brain’s midline. This patient showed no distinct enhancement or clear tumour shape, and there were no significant mass effects. Conversely, the MR images of the younger patient (case 1) revealed a diffuse and infiltrating glioma with extensive peritumoral oedema and pronounced intratumoral haemorrhage. Additional findings included multifocal enhancement, prominent high perfusion, and fibre destruction. The solid mass induced significant mass effects coupled with haemorrhage, indicative of a malignant tumour.

Both patients exhibited similar clinical features, including limb weakness. The patient in case 1 underwent subtotal resection, and the patient in case 2 underwent only a STB. Both patients were subsequently treated with concurrent chemoradiotherapy. As previously mentioned, the patient in case 2 survived for at least 5 months, and the patient in case 1 survived for at least 4 months following resection or STB. According to Lim et al., the median survival time of the patients with H3.3 G34-mutant high-grade gliomas (HGGs) is 23.5 months, which is longer than that of patients with K27M-mutant diffuse midline gliomas (10,12,13). MGMT promoter methylation is considered a biomarker for predicting the response to alkylating agents (14,15); therefore, the identification of MGMT methylation in H3.3 G34R-mutant patients may increase the response to TMZ and thus improve outcomes (12). Both patients in our study exhibited MGMT promoter methylation, which may prolong patient survival. However, they lost contact with us after 4–5 months of follow-up visits. The median survival time of patients with HGGs with H3.3 G34R mutations is longer than that of patients with HGGs with H3 K27M mutations (10). These uniform genetic and epigenetic abnormalities may have value in predicting the prognosis of tumours in patients with H3.3 G34R mutations.

H3.3 G34R-mutant gliomas are known to commonly occur in adolescents and young adults (2,16,17). Several imaging characteristics of gliomas with H3 G34R mutations have been reported in previous studies (Table 1) (2,5,6). However, these studies did not include multimodal MRI features. For the two cases described here, the patients were 13 and 26 years old, which was consistent with the findings of a previous study (3). Moreover, Yoshimoto K et al. revealed that younger (an 8-year-old patient and a 10-year-old patient) patients with H3.3 G34-mutant gliomas presented with marked contrast-enhanced lesions, whereas older patients (an 11-year-old patient and a 37-year-old patient) presented with mild contrast enhancement (3). Similarly, the patient in case 2 (26 years old) showed almost no enhancement, and the patient in case 1 (13 years old) showed remarkable enhancement. These results imply that DHG-G34m might have different structural MR imaging signatures across different age groups. However, the histopathological grade (WHO grade 3 vs. grade 4) may affect the findings on MR imaging. The relationship between age and H3.3 G34R mutation should be further explored.

Conclusions

In summary, the cases of a paediatric patient and an adult patient with H3.3 G34R mutant gliomas were reported in our study. A significant mass effect with pronounced contrast enhancement was observed in case 1, and diffuse hyperintensity on T2-weighted imaging with minimal contrast enhancement was observed in case 2. While the structural imaging profiles of the two cases differed, they shared similar functional MR imaging signatures, such as elevated perfusion and an increased Cho/NAA ratio. These findings suggest that functional MR imaging could assist in the identification of malignant gliomas with atypical features on structural imaging, facilitating the selection of the optimal surgical strategies for patients. Future large-sample investigations with long follow-up period are needed to clarify the effects of the H3.3 G34R mutation on MR signatures.

Acknowledgments

A portion of the textual descriptions in this article has been presented at Chinese Medical Association 2022 National Neuro-Oncology Conference, however, none of the case images have been showcased at any conference.

Funding: This work was supported by the National Natural Science Foundation of China (grant No. 82302160).

Footnote

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://qims.amegroups.com/article/view/10.21037/qims-24-485/coif). The authors have no conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. All procedures performed in this study were in accordance with the ethical standards of the institutional and/or national research committee(s) and with the Helsinki Declaration (as revised in 2013). This study was approved by the Institutional Review Board (IRB) of West China Hospital of Sichuan University (No. 745 of 2023). Written informed consent was obtained from the patient or the patient’s parents for publication of this article and accompanying images. A copy of the written consent is available for review by the editorial office of this journal.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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