Adult medulloblastoma in Japan ~Single institutional case series with literature review~

Medulloblastoma in adults older than 20 years of age is extremely rare disease in Japan. We here report the clinical characteristics, tumor pathology including molecular classification, treatment, and prognosis of 3 cases of patients with adult medulloblastoma, and discuss the clinical issues. Three female patients, aged 28, 35, and 48 years, presented with intracranial hypertension, vertigo and cerebellar ataxia. The tumors, which were relatively well-demarcated and irregularly contrasted were located in the cerebellar vermis in one patient and in the cerebellar hemisphere in the two patients. All patients underwent subtotal or greater resection. The pathological diagnosis was classic type medulloblastoma, and the molecular classification was Group 4, SHH-TP53 wildtype and WNT. Whole-brain and whole-spinal irradiation was performed, followed by ICE (ifosfamide, cisplatin, and etoposide) chemotherapy. Two patients with a hemispheric tumor showed no recurrence and had a favorable clinical course, whereas the patient with a vermis tumor with a small residual tumor in the brainstem developed multiple spinal metastases and cerebrospinal fluid dissemination within 2 years after the surgery. In the EU and the United States, guidelines for the treatment of adult medulloblastoma have been established, which recommend the addition of craniospinal irradiation protocols and multi-agent chemotherapy according to the clinical risk of each patient, determined by the pathological diagnosis and molecular classification. In Japan, there have been only a few case reports of adult medulloblastoma, and both basic and clinical research has not substantially progressed. Therefore, the establishment of medical practice guidelines for adult medulloblastoma urgently needed in Japan.