Radiological imaging plays a pivotal role in glioma patient care. It provides qualitative information about the tumor, such as the presumed pathological diagnosis and molecular status. In addition, it can provide anatomical information necessary for surgery and is helpful for monitoring treatment response. In this review, we discuss the following topics :

 1. The progress in radiomics in the field of glioma.

 2. Detailed analysis of the T2-FLAIR mismatch sign.

 3. The potential of quantitative magnetic resonance (MR) imaging in the realm of qualitative glioma imaging.

  Radiomics “focuses on improvements in image analysis, using an automated high-throughput extraction of large amounts (200＋) of quantitative features of medical images”. Despite extensive research, its diagnostic accuracy for detecting IDH mutations is limited to approximately 85% sensitivity and specificity. The diagnosis of 1p/19q co-deletion is 10% less accurate than that of the IDH mutation. The accuracy for diagnosing MGMT promoter methylation is still uncertain.

  Furthermore, the generalization of diagnostic algorithms derived from machine learning is another critical issue. While many researchers in the community have pushed radiomic research to the limit, a conventional qualitative imaging feature, namely, “the T2-FLAIR mismatch sign,” was discovered. This imaging feature is able to identify IDH-mutant, 1p/19q non-codeleted astrocytomas with a sensitivity of 20-50% and a specificity of almost 100%. Through radiomic research of gliomas, the authors noticed potential effects of differences in image acquisition parameters between different institutions on the low sensitivity of the T2-FLAIR mismatch sign for detecting IDH-mutant and 1p/19q non-codeleted astrocytomas. Indeed, tuning the image acquisition parameters for FLAIR significantly improved the sensitivity of the T2-FLAIR mismatch sign. Finally, the future of MR-based glioma imaging relies on quantitative MR acquisition. This technique directly measures the tissue's T1- and T2-relaxation times, which provides valuable information for cancer tissue characterization. For example, we found that IDH-mutant, 1p/19q non-codeleted astrocytomas contain tissues with very long T1- and T2-relaxation times (longer than 3,000ms in T1-relaxation time). The commercialization of rapid quantitative MR acquisition technology could further boost the capability of radiomics.

  Glioblastoma is the most malignant brain tumor, with a median survival of approximately. two years. Glioblastoma treatment can be broadly divided into three categories : surgery, radiation therapy, and chemotherapy. Removal beyond the contrast-enhanced site has been reported to be better because the removal rate is a prognostic factor. However, it is necessary to emphasize the functional prognosis. Therefore, in addition to conventional intraoperative monitoring, intraoperative fluorescence diagnosis using 5-ALA, awake surgery, and intraoperative magnetic resonance imaging are performed. As intraoperative local therapy, carmustine wafer placement and photodynamic therapy are also performed at the excised part. In addition, temozolomide and bevacizumab are used for chemotherapy, but the optimal timing and method of administration of bevacizumab are still debated. For radiation therapy, short-term irradiation is recommended for elderly patients. In addition, electric field therapy with a novo-TTF device is a new treatment method that suppresses cell division by the force of the electric field. In addition, various treatments including immunotherapy and viral therapy have been devised for the treatment of glioblastoma. This article outlines the findings to help to understand the latest glioma multidisciplinary treatments.

  Primary central nervous system lymphoma (PCNSL) develops more often in the elderly population. Its incidence has been increasing in recent years and it is accounting for 4.9% of brain tumors. Most PCNSLs are histologically classified as diffuse large B-cell lymphomas. Among these, CD10 positivity is lower and MUM1 positivity is higher in PCNSL than in non-PCNSL, which results in higher dominance of the non-germinal-center B-cell-like type in PCNSLs. The frequency of mutations in MYD88 and CD79B genes is higher in PCNSL than in non-PCNSL, which leads to the activation of the B-cell-receptor signaling pathway. Bruton's tyrosine kinase (BTK) is a key molecule in the B-cell-receptor signaling pathway. Therefore, it is a potential molecular target for the treatment of PCNSL. Tirabrutinib, a second-generation BTK inhibitor, has been developed and approved in Japan for the treatment of recurrent or refractory PCNSL. Current challenges include increasing the intensity of chemotherapy while reducing the dose or avoidance of whole-brain radiotherapy (WBRT), as brain damage and late effects, including leukoencephalopathy, are not negligible not only in elderly patients but also in young patients. In Japan, the combination of rituximab, high-dose methotrexate, procarbazine, and vincristine, the so-called R-MPV therapy, is being recognized as a new standard induction chemotherapy. R-MPV therapy followed by reduced-dose WBRT and high-dose cytarabine is well tolerated and shows better outcomes than the previous standard high-dose methotrexate therapy followed by WBRT. High-dose chemotherapy with autologous peripheral blood stem cell transplantation in young patients and appropriate treatment selection at the time of recurrence are essential for further improvement of treatment outcomes.

  Germ cell tumors, which occur predominantly in adolescents and young adults, are composed of various histological types. It is difficult to establish standard treatments because the roles of resection, radiation, and chemotherapy differ with each histological subtype. To date, clinical trials have been conducted in Japan, Europe, and North America, and various diagnostic methods, classifications for proper treatment, and treatment modalities have been established and developed. In parallel with this situation, a consensus regarding their diagnosis and treatment was established by the Delphi method in 2013 by multidisciplinary experts, and the areas that became the consensus and the areas to be discussed became clear to some extent. Based on these circumstances and the current situation, this review outlines problems and recent new findings regarding the diagnosis and treatment of germinomas and nongerminomatous germ cell tumors.

  A 69-year-old woman was treated with immunosuppressive agents (methotrexate, tacrolimus, cyclosporine, etanercept, adalimumab, azathioprine, and mycophenolate mofetil) for a 30-year history of systemic lupus erythematosus, rheumatoid arthritis, and interstitial pneumonia. She presented to our hospital for evaluation of right-sided hemiparesis. Magnetic resonance imaging revealed a ring-enhanced mass lesion (maximum diameter 36mm) in the left parietal lobe. She was hospitalized for further evaluation and treatment of suspected high-grade glioma, metastatic brain tumor, and malignant lymphoma. We performed subtotal tumor resection, and histopathological evaluation of the resected specimen confirmed diagnosis of diffuse large-cell B-cell lymphoma, an iatrogenic lymphoproliferative disease caused by immunosuppressive drugs. This disorder was attributed to mycophenolate mofetil therapy initiated 1 year before symptom onset. Mycophenolate mofetil therapy was discontinued, and the patient received six cycles of rituximab and local radiation. Iatrogenic lymphoproliferative disease is known to occur during mycophenolate mofetil treatment ; however, primary lymphoproliferative disease of the central nervous system associated with mycophenolate mofetil therapy is rare.

  The standard procedure for treating an aneurysmal intracerebral hematoma (ICH) is a concomitant treatment of surgical clipping and ICH evacuation. We report a case of an alternative, minimally invasive strategy using coil embolization for isolating the ruptured aneurysm, followed by neuroendoscopic hematoma evacuation in a hybrid operating room.

  A 52-year-old female patient presented with sudden headache and was admitted to our hospital. Observation revealed subarachnoid hemorrhage (SAH) with intracerebral hematoma in the right frontal lobe caused by a ruptured aneurysm in the left distal anterior cerebral artery. We performed coil embolization of the ruptured aneurysm followed by hematoma evacuation using neuroendoscopy concomitantly in our hybrid operating room. This technique was successful, and the patient recovered and was discharged on day 34 with modified Rankin Scale score of 1.

  Coil embolization followed by neuroendoscopic hematoma evacuation provides an alternative, less invasive treatment strategy in cases of ruptured aneurysms presenting with intraparenchymal hematoma.