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Type:
Educational Exhibit
Keywords:
Cancer, Diagnostic procedure, MR-Spectroscopy, MR, CT, Paediatric, Oncology, CNS
Authors:
J. Sarnecki1, M. Goluch1, M. Łastowska1, W. Grajkowska1, M. Perek-Polnik1, E. Jurkiewicz2; 1Warszawa/PL, 2Warsaw/PL
DOI:
10.1594/ecr2017/C-1789
Background
Medulloblastma (MB) is a highly malignant (WHO grade IV),
primitive cerebellar tumor of neuroectodermal origin [1,2].
It is the most common malignant brain tumor in children and accounts for approximately 30-40% of childhood posterior fossa tumors [1,3].
Medulloblastoma has a moderate male sex predilection (1,5:1) and tends to occur in younger children,
with majority of cases being diagnosed in patients ≤10 years old [3-5].
The 2007 World Health Organization classification of tumors of the central nervous system (CNS) used histology to classify medulloblastomas,
differentiating variants such as ‘classic’ MB (most common),
desmoplastic/nodular MB,
large cell/anaplastic and MB with extensive nodularity (MBEN) [5-7].
As a result of the advances in molecular biology made in the past decade,
it became apparent that the disease consists of 4 distinct,
biologically different,
molecular subgroups: WNT,
SHH,
group 3 and group 4 [2,5-9].
The subgroups are associated with specific genetic features,
demographics and metastatic status and were found to be more predictive of clinical behavior and outcome than the histological classification or clinical staging (with WNT linked to very good,
SHH and group 4 to intermediate and group 3 to poor prognosis) [2,5-9].
Histological variants are not indicative of a molecular subgroup,
however some associations have been observed,
e.g.
all MBENs belong to the SHH subgroup,
though SHH tumors can also present as a ‘classic’ or a desmoplastic/nodular histological variant.
The molecular division of the disease was recognized by WHO in 2016 in its new classification of CNS tumors and immunohistochemistry and sequencing analysis are recommended alongside the histological evaluation of the tumor [7].
Imaging studies play an important role in diagnosing and staging of the disease,
as well as in the assessment of the extent of resection and in the surveillance for the disease recurrence.
Due to its wide availability,
computed tomography (CT) is often the first imaging study performed in children presenting neurological symptoms which suggest a brain tumor.
Nevertheless,
magnetic resonance imaging (MRI) is a superior method,
due to its greater sensitivity compared to CT and the fact that it allows for a more precise assessment of the tumor’s size,
location and neoplastic subarachnoid spread.
These data,
together with information acquired using diffusion weighted imaging (DWI) and MR spectroscopy,
may also provide enough information about the lesion to identify the type of tumor,
or in case of medulloblastoma,
to suggest the molecular subgroup to which it belongs.
MRI is also the modality of choice in the assessment of completeness of resection and in the surveillance for the recurrence of the disease.