pediatrics
Medulloblastoma
Diagnosis of Medulloblastoma
MRI Histologic evaluation of biopsy specimen or entire resected tumor MRI with gadolinium contrast is the test of choice for initial evaluation of possible medulloblastoma. Definitive diagnosis is made using tumor tissue obtained by biopsy or ideally by gross total resection of the tumor at initial presentation. Once the initial diagnosis is established, staging and risk group determination are critical in medulloblastoma. Staging testsinclude MRI of the entire spine Lumbar puncture for cerebrospinal fluid cytology Postoperative brain MRI to assess for any residual tumor Risk assessmentis based on amount of residual tumor and evidence of spread of disease: High risk: Postoperative residual disease is > 1.5 cm2orthere is disseminated microscopic or gross disease. Average risk: Postoperative residual disease is < 1.5 cm2andthere is no dissemination. Molecular grouping is also part of the diagnostic evaluation, and treatments are evolving based on these groups. The major molecular groups for medulloblastoma are WNT-activated, SHH-activated, group 3, and group 4. New subgroups have emerged at a more granular level below the four major molecular groups. (See also the World Health Organization's2021 classification of tumors of the central nervous system.) 