CTNNB1, AXIN1 and APC expression analysis of different medulloblastoma variants

OBJECTIVES: We investigated four components of the Wnt signaling pathway in medulloblastomas. Medulloblastoma is the most common type of malignant pediatric brain tumor, and the Wnt signaling pathway has been shown to be activated in this type of tumor. METHODS: Sixty-one medulloblastoma cases were analyzed for β-catenin gene (CTNNB1) mutations, β-catenin protein expression via immunostaining and Wnt signaling pathway-related gene expression. All data were correlated with histological subtypes and patient clinical information. RESULTS: CTNNB1 sequencing analysis revealed that 11 out of 61 medulloblastomas harbored missense mutations in residues 32, 33, 34 and 37, which are located in exon 3. These mutations alter the glycogen synthase kinase-3β phosphorylation sites, which participate in β-catenin degradation. No significant differences were observed between mutation status and histological medulloblastoma type, patient age and overall or progression-free survival times. Nuclear β-catenin accumulation, which was observed in 27.9% of the cases, was not associated with the histological type, CTNNB1 mutation status or tumor cell dissemination. The relative expression levels of genes that code for proteins involved in the Wnt signaling pathway (CTNNB1, APC, AXIN1 and WNT1) were also analyzed, but no significant correlations were found. In addition, large-cell variant medulloblastomas presented lower relative CTNNB1 expression as compared to the other tumor variants. CONCLUSIONS: A small subset of medulloblastomas carry CTNNB1 mutations with consequent nuclear accumulation of β-catenin. The Wnt signaling pathway plays a role in classic, desmoplastic and extensive nodularity medulloblastoma variants but not in large-cell medulloblastomas.

Immunohistochemical expression of markers Ki-67, neun, synaptophysin, p53 and HER2 in medulloblastoma and its correlation with clinicopathological parameters / Expressão imunoistoquímica dos marcadores Ki-67, neun, sinaptofisina, p53 e HER2 em meduloblastoma e sua correlação com os parâmetros clínico-patológicos

Medulloblastoma (MB) is the most common malignant brain tumor in childhood. The alterations found include: presence of oncoproteins p53 and HER2, elevated mitotic index, and presence of neuronal differentiation. The aim of this study was to determine the immunohistochemical expression of markers Ki-67, NeuN, synaptophysin, HER2 and p53 in 40 MB samples and their correlation with clinicopathologic parameters and survival. In 29 patients (72.5 percent), >20 percent of cells were positive for Ki-67. Males showed greater ki-67 expression (p=0.02) and smaller survival rates (p=0.002). NeuN and synaptophysin were negative in 16 (40 percent) and 8 (20 percent) cases, respectively. P53 was positive in 18 (45 percent) cases, with 11 (61 percent) weakly positive and 7 (39 percent) strongly positive. HER2 was positive in 23 (57.5 percent) of the samples and did not show statistical association with survival (p=0.07).

Meduloblastoma (MB) é o tumor maligno encefálico mais freqüente na infância. dentre as alterações encontradas estão: a presença das oncoproteínas p53 e HER2, elevado índice mitótico e presença de diferenciação neuronal. o objetivo deste estudo foi determinar a expressão imunoistoquímica (IMQ) dos marcadores Ki-67, NeuN, sinaptofisina, HER2 e p53 em 40 amostras de MB, correlacionando-as com parâmetros clinicopatológicos e com a sobrevida. Vinte e nove pacientes (72,5 por cento) apresentaram 20 por cento ou mais das células positivas para Ki-67. os pacientes do sexo masculino apresentaram maior expressão do Ki-67 (p=0,02) e também menor sobrevida (p=0,002). NeuN e sinaptofisina foram negativos em 16 (40 por cento) e 8 (20 por cento) casos, respectivamente. P53 foi positivo em 18 (45 por cento) casos, sendo 11 (61 por cento) fracamente positivos e 7 (39 por cento) fortemente positivos. HER2 foi positivo em 23 (57,5 por cento) das amostras e não demonstrou associação estatística com a sobrevida (p=0.07).

Cerebellar hemisphere, an uncommon location for pleomorphic xanthoastrocytoma and lipidized glioblastoma multiformis.

Lipidized glioblastoma multiformis (LGB) and pleomorphic xanthoastrocytoma (PXA) are often supratentorial in location and occur in the second to fourth decade. This report presents two young patients, one having LGB and the other having PXA in the cerebellum. Histological differentiation between LGB and PXA is discussed.