Oncogene amplification in medulloblastoma: analysis of a case by comparative genomic hybridization and fluorescence in situ hybridization

We describe amplification of the MYCC oncogene in a medulloblastoma with aggressive clinical behavior. The patient was a six year old boy who underwent gross total surgical excision of a cerebellar tumor. Despite chemotherapy and total neuraxis radiation, the clinical course was one of relentless progression, with extensive subarachnoid spread and death within eight months of presentation. The pathological features were consistent with the recently described, "large cell variant" of medulloblastoma. Tumor cells exhibited large vesicular nuclei, prominent nucleoli and strong immunoreactivity for synaptophysin. Polymerase chain reaction (PCR) and fluorescence in situ hybridization (FISH) assay revealed no evidence of MYCN amplification or 1p deletion in the tumor. FISH analysis revealed evidence of MYCC amplification in the 20- to 30-fold range. Comparative genomic hybridization (CGH) revealed regions of gains and amplification in three locations, with gains of chromosome 7, amplification of 8q24 (corresponding to the MYCC locus) and gains of the long arm of chromosome 17 (suggestive of isochromosome 17q). While conventional karyotypic analysis was not successful in the present case, CGH provided invaluable information about gene amplification and losses/gains of chromosomes and chromosomal regions. Thus, CGH is a powerful technique applicable to frozen or paraffin-embedded material which helps to ascertain the presence of gene amplification even without prior knowledge of the gene to be tested.

Involution of enhancing intrinsic tectal tumors after endoscopic third ventriculostomy. Report of two cases

For benign intrinsic tectal tumors causing triventricular obstructive hydrocephalus, cerebrospinal fluid diversion followed by neuroimaging is a widely accepted treatment plan. In this report, the authors describe two children with focal enhancing tectal lesions that caused acute, symptomatic hydrocephalus. One child had neurofibromatosis Type 1 (NF1). In both children the hydrocephalus was effectively treated by endoscopic third ventriculostomy. Following this procedure, serial imaging studies revealed not only that the ventriculomegaly had resolved, but also that the enhancing tectal tumors had regressed and disappeared over time. The time to complete involution of these tumors was 18 months for the child with NF1 and 12 months for the other child. To the authors' knowledge, this is the first report of the involution of enhancing tectal tumors after endoscopic third ventriculostomy. The possible mechanisms for this unexpected result are discussed.

Ganglioglioneurocytoma of the posterior fossa

OBJECTIVE AND IMPORTANCE

Ganglioglioneurocytoma is not yet a well defined clinical and histopathological entity; recent reports outline the histopathological features of this very rare trimorphous tumor, under different names with its basic components of gangliocytoma, neurocytoma and glioma. Four previous reports described this tumor in eleven patients. This is the first case report describing ganglioglioneurocytoma in the posterior fossa.

CLINICAL PRESENTATION AND INTERVENTION

A 31-year old male with midline posterior fossa ganglioglioneurocytoma is described, providing the neuroimages and histopathological studies.

CONCLUSION

Ganglioglioneurocytoma is a rare mixed neuronal and glial tumor that can also occur in the posterior fossa.

Cytology of pituitary thyrotroph hyperplasia in protracted primary hypothyroidism

Pituitary thyrotroph hyperplasia, a rare cause of pituitary enlargement, is usually associated with protracted primary hypothyroidism. We present here a case of pituitary thyrotroph hyperplasia in a 51 year old woman who was thought to have a pituitary macroadenoma with suprasellar extension. The cytologic investigation of the intraoperative touch preparation identified hyperplastic thyrotrophs, provided the correct diagnosis and helped to limit further aggressive surgical removal of the lesion, which is known to regress after adequate thyroid hormone replacement therapy. This is the first study to describe the cytologic features of pituitary thyrotroph hyperplasia confirmed subsequently by histology, immunocytochemistry and transmission electron microscopy.