In 2021, the World Health Organization (WHO) released the fifth edition of the Classification of Tumors of the Central Nervous System (1). In this updated edition, IDH-mutant glioblastoma, formerly known as “secondary glioblastoma”, is now described as IDH-mutant, grade IV astrocytoma. Additionally, astrocytoma with IDH-mutant grade III and synonymous CDKN2B and/or CDKN2A deletions were also characterized as astrocytoma, IDH mutations, grade IV, albeit with a relatively low histopathologic grade (1, 2). The detailed interaction mechanism between IDH1/2 and CDKN2A/B remains unclear at the biomolecular level. Current research has focused more on the discrepancies between grade 4, IDH-mutant astrocytoma, and glioblastoma (3–6). Few clinical studies have been conducted specifically on this phenotype, and current knowledge remains limited (5).

The simultaneous presence of multiple foci, remarkably homologous foci with different histopathologic compositions, is rare in all types of gliomas (7). Based on radiologic and/or pathologic features, complicating lesions can be divided into multifocal and multicentric categories (8). Multicentric gliomas fail to differentiate due to genetic defects in stem cells, resulting in defective, highly proliferative cell populations that form tumor centers (9). Multifocal gliomas, on the other hand, represent the presence of multiple tumor foci that are differentially associated and have consistent genetic variants (8). Due to this rarity, the underlying molecular relationships of synchronous lesions are poorly understood. Thus far, despite the worse prognosis of multifocal/multicentric gliomas, their treatment is roughly the same as for single lesions (9).

The co-occurrence of astrocytoma of different molecular and histologic classifications at initial diagnosis in a single individual has never been previously described in the literature. We emphasized the importance of integrated genetic and pathology analysis for synchronous gliomas.

The patient, a previously healthy 53-year-old woman, attended a local clinic with a progressive headache accompanied by nonprojectile vomiting. Later, the patient’s symptoms worsened, and she developed weakness in the left limb. She underwent an MRI scan, which showed occupational hemorrhage in the right frontal lobe and basal ganglia region and blood accumulation in the knee of the corpus callosum with subcerebral falciform herniation. The larger lesion was located in the right parietal lobe, showing signs of isometric T1-weighted images (T1WIs) and T2WIs and contrast enhancement with peri-lesion edema and midline shift, size approximately 5.1*4.2*3.7 cm³ ( Figures 1A, B ). The other lesion was a saccular mass located in the right frontal lobe ( Figures 1C ). Several nodular, clustered bands of edema with hyperintensity on fluid-attenuated inversion recovery (FLAIR) images and diffusion-weighted imaging (DWI) were seen ( Figures 1D–G ). She subsequently underwent a navigation-guided trans-frontal craniotomy using electrophysiology to detect functional brain areas. A sub-total resection (STR) was performed to avoid causing dysfunction in the basal ganglia region. Intraoperative ultrasound was used to assess tumor resection. Postoperatively, the patient’s left-sided muscle strength recovered from grade II to grade IV, and MRI revealed minimal contrast enhancement of residual lesions ( Figure 1H ).

Histopathological analysis of the parietal lesion demonstrated a WHO grade IV IDH-mutant diffuse astrocytoma with mesenchymal vascular, endothelial cell proliferation, and palisading necrosis. Microscopically, the cells were dense, tightly arranged, and of variable size, coarse chromatin, visible nucleoli, and nuclear schizophrenia was atypical ( Figures 2A, B ). The cells were positive for GFAP, IDH1, Olig-2, NeuN, Nestin, NF, S100, CD34, SYN, EMN, and Vimentin, but negative for ATRX by immunohistochemistry. The Ki-67 proliferation index was significantly increased, labeling up to approximately 55% of tumor cells. Most cells showed strong p53 staining (80%), and immunofluorescence of EGFR was positive. Detection of CDKN2A/B by fluorescence in situ hybridization (FISH) suggested non-purifying deletions ( Figures 2C, D ). PCRR-Fluorescent with QIAamp FFPE Tissue Kit confirmed the presence of IDH1 R132 mutation and revealed no TERT promoter mutations ( Table 1 , Supplementary Figure S1 ). Pathological diagnosis of the frontal lesion was a WHO grade II IDH-NOS (Isocitrate Dehydrogenase-Not otherwise specified) diffuse astrocytoma without necrosis and microvascular proliferation ( Figures 2E, F ). The Ki-67 proliferation index was slightly increased, marking approximately 2% of tumor cells. The cells were positive for p53, and ATRX staining was not observed ( Supplementary Figure S2 ). The patient tolerated the operation well, continued to improve clinically, and achieved a Karnofsky Performance Scale (KPS) score of 80 at discharge. The patient will then be treated one month later with concurrent temozolomide (TMZ) and radiation, the standard Stupp regimen. Based on follow-up MRI, the patient is currently in a tolerable disease state ( Supplementary Figure S3 ).

In this study, we describe the first case of a patient with two adjacent but histologically distinct primary gliomas at initial treatment. The most notable finding was a WHO grade IV diffuse astrocytoma with the IDH1 R132 mutation in the right parietal basal ganglia region pathology, which differed from the WHO grade II astrocytoma, IDH-NOS found in the right frontal lobe lesion.

This discovery raises two possible pathogenic mechanisms. One speculation is that the right parietal lesion is a secondary lesion derived from the frontal tumor. The different IDH mutations may suggest an evolved trajectory resulting in more invasive clones able to metastasize transmission (8, 10). In this case, glioma cells in the parietal lesion probably possess a more remarkable ability to metastasize through cerebrospinal fluid or cortical tract fibers. Another speculation is the existence of two separate and synchronously evolving multicentric tumors. Higher proportions of IDH1 mutations have been reported in low-grade astrocytomas compared with those in primary glioblastomas and oligodendrogliomas (11–13). Considering this may be an early clonal mutation, different IDH1 mutations may indicate the simultaneous progression of two separate low-grade gliomas (14). In 1996, Watanabe et al. reported the presence of distinct genetic alterations in what were previously called primary and secondary glioblastomas (15). EGFR alterations are prevalent in primary glioblastoma but infrequent in secondary glioblastoma. P53 mutations are much more common in secondary glioblastoma but rare in primary glioblastoma. Interestingly, both p53 (80% positive) and EGFR alterations were detected in the right parietal lesion. But we do not suggest that these two lesions are bi-primary or completely separate tumors since they share the same P53 and ATRX mutations and are anatomically adjacent. The discoveries suggest that ATRX and P53 mutations may first appeared in glial precursor cells. Afterwards, these cells acquired EGRF mutations and became grade IV diffuse astrocytoma. The remaining cells turned into IDH-NOS grade II astrocytoma. This case suggests that IDH mutations could subsequently occur after other genetic changes. In 2020, Yoon et al. made a similar point (16). In their case, the new lesion was diagnosed as glioblastoma six years after a surgical of IDH-mutant diffuse astrocytoma. In recent years, exosomes have been found to perform an important role in intercellular communication, and exosomes secreted by cancer cells have a powerful ability to alter the distant and local microenvironment (17). We speculate that glioma cells in the frontal and parietal lesions may communicate via nanoscale vesicles in neurons and glial cells.

A literature search identified only two published cases of oligodendrogliomas WHO grade-2 and astrocytomas WHO grade-2 (18). Singha et al. described two similar patients with seizure who suffered from oligodendrogliomas of the left parietal lobe and astrocytomas of the right frontal lobe (18). At 6-month follow-up, the patients’ imaging and clinical status remained stable. However, they only performed routine pathological examinations and immunohistochemical tests and did not provide molecular profiling to demonstrate the different biological backgrounds of the two gliomas reported.

Another critical point is the impact of the novel WHO classification in 2021 on clinical care compared to the WHO classification in 2016 (1, 19). Before this update, the patient’s right parietal tumor was classified as an IDH-mutant glioblastoma and, therefore, should receive a gross tumor resection and adjuvant chemotherapy and radiotherapy (20). Based on the latest 2021 WHO classification, the tumor is currently classified as a WHO grade IV IDH-mutant diffuse astrocytoma. Considering her health condition, we performed a sub-total tumor resection.

We report here a rare case of adjacent multifocal diffuse astrocytoma with distinct WHO grades, IDH mutations, and biological background. A combination of molecular and histologic parameters uncovered distinct clonal origins of the two lesions. We also highlighted the differences between the 2016 WHO classification and the updated 2021 version regarding glioma classifications.

The original contributions presented in the study are included in the article/Supplementary Material. Further inquiries can be directed to the corresponding author.

The participants provided their written informed consent for the publication of their potentially-identifying data and/or images.

FJ: Writing – original draft, Writing – review & editing. YK: Conceptualization, Investigation, Software, Writing – review & editing. ZW: Data curation, Methodology, Supervision, Writing – original draft.