A 14-year-old boy presents with nausea, vomiting, generalized headache, ataxia, and visual complaints. The headaches have awoken him nightly for the past six weeks. MRI reveals a cystic tumor in the cerebellum. Biopsy of the tumor reveals a well-differentiated neoplasm comprised of spindle cells that have hair-like glial processes and are associated with microcysts. These cells are mixed with Rosenthal fibers and granular eosinophilic bodies. Based on these findings, the most likely diagnosis is which of the following?

Question

A 14-year-old boy presents with nausea, vomiting, generalized headache, ataxia, and visual complaints.  The headaches have awoken him nightly for the past six weeks.  MRI reveals a cystic tumor in the cerebellum.  Biopsy of the tumor reveals a well-differentiated neoplasm comprised of spindle cells that have hair-like glial processes and are associated with microcysts.  These cells are mixed with Rosenthal fibers and granular eosinophilic bodies.  Based on these findings, the most likely diagnosis is which of the following?

Quizplus · Accepted Answer

Juvenile pilocytic astrocytomas usually arise in the cerebellum, brainstem, hypothalamic region, or optic pathways. Microscopically, pilocytic astrocytomas are well-differentiated neoplasms comprised of spindle cells with hair-like glial processes that are associated with microcysts. These cells are mixed with Rosenthal fibers and granular eosinophilic bodies. (Choice B) GBMs occur most often in the subcortical white matter of the cerebral hemispheres. When a tumor in the frontal cortex spreads across the corpus callosum into the contralateral hemisphere, it creates the appearance of a bilateral symmetrical lesion, hence the term "butterfly glioma." GBMs are composed of poorly-differentiated, often-pleomorphic astrocytic cells with marked nuclear atypia and brisk mitotic activity. Necrosis is an essential diagnostic feature, and prominent microvascular proliferation is common. (Choice C) Medulloblastoma (primitive neuroectodermal tumor, or PNET) is the second most common posterior fossa tumor in children. On microscopic examination, cells are small and poorly differentiated, with scant cytoplasm and little stroma. A high mitotic index is common. Classic Homer-Wright rosettes can be seen in one fifth of cases. (Choice D) Ependymomas account for 10% of posterior fossa tumors in children. Intracranial lesions usually occur infratentorially, arising from the roof of the fourth ventricle in children, while spinal ependymomas typically occur in adults. Histologically, ependymal pseudorosettes with glial fibrillary acidic protein (GFAP)-positive processes tapering toward blood vessels characterize ependymomas. (Choice E) Neuroblastomas are the most common extracranial solid tumors occurring in children. Undifferentiated neuroblastomas are small, round, blue-cell tumors. A neuritic process, also called neuropil, is a pathognomonic feature of neuroblastoma cells. NSE, chromogranin, synaptophysin, and S-100 immunohistochemical stains are usually positive. More than 90% of patients have elevated urinary levels of homovanillic acid (HVA) and/or vanillylmandelic acid (VMA). The most important biologic marker is MYCN (N-MYC) of chromosome 2. Educational Objective: A cystic tumor in the cerebellum of a child is most likely a pilocytic astrocytoma. Biopsy will show a well-differentiated neoplasm comprised of spindle cells with hair-like glial processes that are associated with microcysts. These cells are mixed with Rosenthal fibers and granular eosinophilic bodies.

A 14-Year-Old Boy Presents with Nausea, Vomiting, Generalized Headache, Ataxia