Ganglioglial differentiation in medulloblastoma

Post-treatment maturation of medulloblastoma in children: two cases and a literature review

We herein report two cases of post-treatment maturation of medulloblastoma (MB). We also conducted a literature review to summarize the clinical and pathologic features of MB maturation. From January 1992 to February 2017, 52 patients with MB underwent surgical resection followed by radiotherapy and chemotherapy. Tumor cell maturation was identified in two patients who underwent a second surgery. We conducted a systematic search of PubMed and identified six such cases. In both of our patients, the pathologic type was MB with extensive nodularity (MBEN). Both patients underwent radiotherapy and chemotherapy. The tumor differentiated to gangliocytoma in both patients. In the overall analysis that also included the six cases identified in the literature, the pathologic types were classic MB (n=1), desmoplastic/nodular MB (n=2), MBEN (n=3), and unclassified MB (n=2). MB differentiated into the following types: gangliocytoma (n=2), ganglioglioma (n=1), melanocyte (n=1), neuronal differentiation (n=2), and classic MB (n=1). Desmoplastic/nodular MB and MBEN can differentiate into less malignant cells types after radiotherapy and chemotherapy. Maturation of MB may be affected radiotherapy and chemotherapy.

Pleiotropic role for MYCN in medulloblastoma

Medulloblastoma (MB) is the most common malignant brain tumor of childhood. Sonic Hedgehog (SHH) signaling drives a minority of MB, correlating with desmoplastic pathology and favorable outcome. The majority, however, arises independently of SHH and displays classic or large cell anaplastic (LCA) pathology and poor prognosis. To identify common signaling abnormalities, we profiled mRNA, demonstrating misexpression of MYCN in the majority of human MB and negligible expression in normal cerebella. We clarified a role in pathogenesis by targeting MYCN (and luciferase) to cerebella of transgenic mice. MYCN-driven MB showed either classic or LCA pathologies, with Shh signaling activated in approximately 5% of tumors, demonstrating that MYCN can drive MB independently of Shh. MB arose at high penetrance, consistent with a role for MYCN in initiation. Tumor burden correlated with bioluminescence, with rare metastatic spread to the leptomeninges, suggesting roles for MYCN in both progression and metastasis. Transient pharmacological down-regulation of MYCN led to both clearance and senescence of tumor cells, and improved survival. Targeted expression of MYCN thus contributes to initiation, progression, and maintenance of MB, suggesting a central role for MYCN in pathogenesis.

Cerebellar medullomyoblastoma with advanced neuronal differentiation and hamartomatous component

This report describes an unusual medullomyoblastoma which developed in the cerebellar vermis of a 6-year-old girl. Histological investigation showed a highly cellular and predominantly undifferentiated tumor. Myogenic differentiation was prominent in clusters of large tumor cells with eosinophilic cytoplasm and immunoreactivity for desmin and myoglobin. Electron microscopy revealed the presence of immature Z-bands. Immunohistochemically, numerous cells showed incipient expression of myoblastic marker antigens, supporting the view that medulloblastomas and related primitive neuroectodermal tumors possess the potential for non-neural differentiation. In addition, there was evidence of advanced neuronal differentiation, with expression of neuron-specific enolase, synaptophysin, retinal S-antigen, and the formation of ganglioid tumor cells. Occassional neoplastic cells expressed glial fibrillary acidic protein without morphologically detectable astrocytic differentiation. Associated with the neoplasm was brain tissue containing clusters of neuronal cells and focal accumulations of immature oligodendroglia-like cells which expressed neuronal marker antigens. This unusual component resembled a hamartomatous lesion and would support the hypothesis that the cerebellar medullomyoblastoma originated from a teratomatous or malformative lesion. Alternatively, this component may constitute the end stage of advanced neuronal differentiation of a primitive neuroectodermal tumor.