Resection was performed.
Paraffin sections show fragments of a densely hypercellular tumor. Tumor cells have markedly pleomorphic nuclei, some with delicate processes and are arranged predominantly in diffuse sheets in a fibrous stroma. Scattered Homer-Wright rosettes are noted. An occasional mitotic figure is identified. There is no microvascular proliferation and no necrosis is seen. Attachment of leptomeninges is noted. The tumor cells are diffusely synaptophysin and CD56 positive. Patchy staining for NeuN and GFAP.
Topoisomerase index (Cellular proliferation index ) is about 25%.
Medulloblastoma (WHO Grade IV)
Medulloblastoma can be divided into histologic subtypes:
- Classic (Most common, more than two thirds)
- Anaplastic/large cell (Least common, less than 10%).
There are also four established molecular subgroups (based on molecular markers of the tumor), which are becoming more important to clinical practise: WNT (wingless), SHH (sonic hedgehog) and the non WNT/SHH groups (groups 3 and 4). WNT has the best prognosis while group 3 has the worst prognosis.