Diagnosis of Medulloblastoma
It is estimated that 140 adults (age 15 and older) are diagnosed each year in the United States and around 220 children (cancer.org). While adult forms of medulloblastoma are not characteristically defined in subtypes, with childhood medulloblastoma they can be subdivided into the following subtypes:
- WNT-activated – WNT-activated group is the best known of the medulloblastoma subgroups and typically has an improved long term prognosis. This classification is frequently described as having CTNNB1 mutations, nuclear immunohistochemical staining for β-catenin, and monosomy six (deletion of one copy of chromosome 6 in the tumor).
- SHH-activated - The Shh group of medulloblastomas are named after the Sonic Hedgehog signaling pathway, which is thought to drive tumor initiation in many, if not all such cases. Individuals with germline mutations in the Shh receptor PTCH have Gorlin syndrome, which includes a predisposition to medulloblastoma
- Group 3 (non-WNT/non-SHH) - Group 3 tumors are mostly classic medulloblastomas, although they do encompass the majority of the LCA tumors. The current gold standard for diagnosis of a Group 3 tumor is a transcriptional profile that clusters with other Group 3 tumors. Group 3 tumors occur more commonly in males than females, and are found in infants and children, but are almost never observed in adults. Group 3 tumors have a high incidence of LCA histology, and are very frequently metastatic.
- Group 4 (non-WNT / non-SHH) - Group 4 medulloblastomas are the prototypical medulloblastoma. As the molecular pathogenesis of Group 4 tumors is not currently clear, the generic name ‘Group 4’ has been chosen for the current consensus nomenclature pending further insights. Currently, Group 4 medulloblastomas are identified through a transcriptional profile that clusters with other Group 4 medulloblastomas.
Medulloblastoma is more common in children. In adults, medulloblastoma typically affects younger adults between 20 and 40 years of age. Medulloblastoma occurs more often in males than females.
Typically medulloblastoma is diagnosed by magnetic resonance imaging (MRI) and a contrasting image. After diagnosis, it is normal that full MRI of the spinal cord is recommended to determine if it has spread. Additionally, your doctor may perform a neurological exam to determine which part of the brain may be affected by the tumor, a tissue sample or biopsy to refine imaging results, or a lumbar puncture to examine tumor cells or other abnormalities.
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