(BQ) Part 2 book "Brain tumors" presentation of content: Extraventricular neurocytoma, paraganglioma, pineal parenchymal tumor of intermediate differentiation, classic medulloblastoma, desmoplastic medulloblastoma, anaplastic medulloblastoma, cellular schwannoma, melanotic schwannoma,. and other content. | Case 45: Extraventricular Neurocytoma C L I N I C A L I N F O R M AT I O N The patient is a 27-year-old female who is found to have papilledema following work-up for headaches. An MRI scan shows a large left parieto-occipital cyst with an enhancing mural nodule. She undergoes complete gross total excision of the lesion. OPINION Sections show a calcified, cytologically bland, moderately hypercellular neoplasm, devoid of necrosis or microvascular proliferation. Numerous hyalinized blood vessels are present throughout the tumor, as is focal hemosiderin pigment. The tumor demonstrates diffuse positive staining, with synaptophysin antibody. We consider the lesion to be a low-grade neurocytic tumor and characterize it as follows: Left F I G U R E 4 5 . 1 Lower-magnification appearance of the tumor, demonstrating moderate hypercellularity, hyalinized blood vessels, and vague orientation of tumor cells around blood vessels. Parieto-Occipital Region, Excision–Extraventricular Neurocytoma, WHO Grade II. COMMENT Given the fact that this tumor did not occur within the ventricular system, this neoplasm—which is otherwise histologically identical to central neurocytoma—would be considered an extraventricular neurocytoma. The cystic nature is apparent only on the neuroimaging studies, because the pathologist receives the solid mural nodule portion of the tumor. DISCUSSION Extraventricular neurocytoma is a new entity in the 2007 World Health Organization classification system. Although both central neurocytoma and extraventricular neurocytoma are composed of FIGURE Intermediate magnification shows the neuropil-like fibrillary background, as well as the slight variability in size of tumor nuclei. 134 135 CASE 45: E X T R AV E N T R I C U L A R FIGURE High-power magnification depicts the salt-andpepper chromatin pattern of the nuclei and scant cytoplasm. “uniform round cells that show immunohistochemical and ultrastructural features of neuronal differentiation”
