The classic rosette with tumor cells around a central lumen can be seen.In the past, medulloblastoma was classified using histology, but recent integrated genomic studies have revealed that medulloblastoma is composed of four distinct molecular and clinical variants termed WNT/β-catenin, Sonic Hedgehog, Group 3, and Group 4. Of these subgroups, WNT patients have an excellent prognosis and group 3 patients have a poor prognosis. Also, a subgroup-specific alternative splicing further confirms the existence of distinct subgroups and highlights the transcriptional heterogeneity between subgroups. Amplification of the Sonic Hedgehog pathway is the best characterized subgroup, with 25% of human tumors having mutations in Patched, Sufu (Suppressor of Fused Homolog), Smoothened, or other genes in this pathway. Medulloblastomas are also seen in Gorlin syndrome as well as Turcot syndrome. Recurrent mutations in the genes CTNNB1, PTCH1, MLL2, SMARCA4, DDX3X, CTDNEP1, KDM6A, and TBR1 were identified in individuals with medulloblastoma. Additional pathways disrupted in some medulloblastomas include MYC, Notch, BMP, and TGF-β signaling pathways. Diagnosis
The tumor is distinctive on T1- and T2-weighted MRI with heterogeneous enhancement and a typical location adjacent to and extension into the fourth ventricle. Histologically, the tumor is solid, pink-gray in color, and is well circumscribed. The tumor is very cellular, with high mitotic activity, little cytoplasm, and a tendency to form clusters and rosettes. The Chang staging system can be used in making the diagnosis [1]. Correct diagnosis of medulloblastoma may require ruling out atypical teratoid rhabdoid tumor. Treatment
Treatment begins with maximal surgical removal of the tumor.
The hormonal and intellectual deficits created by these therapies causes significant impairment of the survivors.In current clinical studies, the patients are divided into low-, standard- and high-risk groups:

Depending on the study, healing rates of up to 100% are achieved in the low-risk group (usually WNT-activated). The current efforts are therefore moving in the direction of reducing the intensity of the therapy and thus the negative long-term consequences while confirming the high healing rates. In the HIT-SIOP PNET 4 study, in which 340 children and adolescents of the standard-risk group between the ages of four and 21 from several European countries participated, the 5-year survival rate was between 85% and 87% depending on the randomization. Around 78% of the patients remained without relapse for 5 years and are therefore considered to be cured. After a relapse, the prognosis was very poor. Despite intensive treatment, only four of 66 patients were still alive 5 years after a relapse. A US study involved 161 patients between the ages of three and 21 with a high-risk profile. Depending on the randomization, half of the patients additionally received carboplatin daily during the radiation. The 5-year survival rate of patients with carboplatin was 82%, those without 68%. The European SIOP PNET 5 study is currently taking place and will run until April 2024, in which an attempt is made to confirm the promising results with carboplatin during irradiation in the standard risk group. Epidemiology
Medulloblastomas affect just under two people per million per year, and affect children 10 times more than adults.