Comparision of Myc C protooncogene amplification between different morphological areas in medulloblastomas

Medulloblastoma is primitive neuroectodermal tumor of the cerebellum.Although it is very rare in adults, it is the most common malignant brain tumor in children.Researchs concerning the prognosis of the medulloblastomas and maintaining the risk groups of patients have been continuing because of the heterogenicity seen in the histopathological properties, molecular profiles and clinical behaviours of the medulloblastomas.We aimed to investigate the existance of amplification of Myc C protooncogene, in different histopathological areas of the same tumor and its role in tumor progression, to define the morphological properties of the tumor, to compare the prognosis of the patients with both Myc C oncogene amplification and the morphological properties. Furthermore, the clinical and histopathological differences between adult and pediatric cases were taken into consideration.In our study we examined 29 medulloblastomas, 13 of them were adults and 16 of them were pediatric cases. Histopathologic subclassification was done as 2007 WHO classification. FISH is applied to all cases in order to detect Myc C protooncogene.In our study, we concluded that most of the medulloblastoma cases were seen in pediatric age, and more common in male gender. It is confirmed that the prognosis is worse in pediatric cases than in adult cases. Although the tumor is usually located in vermis, both hemispheres are more predisposed to be involved in adults.Classical type is the most common histological subtype of medulloblastomas. LC/A MB is the subtype related to worse prognosis and most deaths are reported with this subtype. In our study, we detected Myc C protooncogene amplification in 2 of 29 cases (6.9%) both were LC MB subtype. The existance of metastasis at the time of diagnosis and lost of the case in the early postoperative period strengthens the feature of Myc C protooncogene amplification as a bad prognostic molecular determinant, as seen in our pediatric case which was also in the high risk group.Even though it is considered that focal anaplastic focus particularly accompany to the classical subtype and reflects the histological progression, in our study none of the tumors containing focal anaplastic focus showed Myc C amplification by FISH.Glial differantiation, myogenic and melanotic differantiation, rosette/pseuodorosette formation, calsification, vascular endothelial proliferations are the morphological properties of medulloblastomas. Mitosis usually accompany with LC/A MB. It is considered that high mitotic activity shows the characteristics of anaplastic medulloblastomas and serves as a useful parameter during subtyping.Worse clinical prognostic parameters, in medulloblastomas are determined as the existance of metastasis at the time of diagnosis and being in the high risk group besides patient age.In conclusion, medulloblastoma is a malignant tumor which has an aggressive course particularly in the pediatric group. Researchs are continuing on many factors affecting the prognosis of medulloblastoma in order to increase the possibility to treat the patients. In this study, some of histopatological properties and the prognostic significance of Myc C protooncogene amplification in the molecular aspect is tried to be revealed. Myc C protooncogene amplification is ascertained to be related to a worse clinical history as accompanying to histological subtypes and worse clinical prognostic factors. But we are unable to show Myc C protooncogene amplification in any anaplastic foci to support the role of Myc C amplification in tumor progression.Key Words: Medulloblastoma, Myc C, Amplification