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21/30. Chromosome 17 abnormalities in pediatric neuroblastic tumor with abundant neuropil and true rosettes.

    Although as a group, embryonal central nervous system tumors share a common background of primitive round cells, numerous distinctive histologic features allow for further subclassification. One tumor with a unique microscopic appearance is the recently described pediatric neuroblastic tumor with abundant neuropil and true rosettes (PNTANTR). We report 2 additional cases of this unusual tumor; both arose in 4-year-old children, one a midpontine tumor and the other a large cerebral lesion. The tumors contained hypercellular sheets of undifferentiated cells, broad zones of neuropil, and scattered perivascular, Homer Wright, and multilayered ependymoblastic-like rosettes. Isochromosome 17q was detected in multiple samples from one tumor, while the other tumor showed polysomy 17. No deletions of INI1 or amplifications of MYC or MYCN were detected. This report adds 2 cases to our experience of PNTANTR and is the first to demonstrate isochromosome 17q, a molecular alteration typical of medulloblastomas.
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22/30. rhabdoid tumor of the kidney with primitive neuroectodermal tumor of the central nervous system: associated tumors with different histologic, cytogenetic, and molecular findings.

    rhabdoid tumor of the kidney (RTK) is associated with tumors of the central nervous system (CNS) in approximately 15% of cases. We describe the clinical features, histologic and cytogenetic findings, and molecular analysis of renal and CNS tumors from the same patient. The histology of the renal tumor was consistent with rhabdoid tumor. The CNS tumor was a primitive neuroectodermal tumor (PNET). The karyotype of the RTK was normal male. The PNET of the brain demonstrated monosomy 22 as the only cytogenetic abnormality, similar to reported cases of malignant rhabdoid tumor of the brain, but dissimilar to nonrandom cytogenetic findings in other CNS PNETs. Molecular cytogenetic and dna marker studies confirmed loss of chromosome 22 in this patient's brain tumor. dna allelotyping showed retention of both parental chromosome 22 alleles in the RTK and loss of the maternal allele in the PNET. Evaluation of additional RTKs and brain tumors occurring in the same patient may provide insight into the origins and relationships of these enigmatic tumors.
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23/30. Primary central nervous system malignant rhabdoid tumor: CT and MR appearance simulates a primitive neuroectodermal tumor.

    Malignant rhabdoid tumor was originally described and is most commonly reported in the kidney [1-5]. A case of primary central nervous system malignant rhabdoid tumor is presented. The clinical and pathologic findings are presented and the computed tomography and magnetic resonance imaging findings are described.
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24/30. Gliomas in patients with acquired immune deficiency syndrome.

    BACKGROUND. Ten percent of patients with acquired immune deficiency syndrome (AIDS) have intracerebral mass lesions of which the majority are due either to toxoplasmosis or primary central nervous system lymphomas. methods. Three patients with AIDS presented with solitary intracerebral mass lesions and were found by pathologic examination to have gliomas. RESULTS. After surgery, all patients were treated with radiotherapy and procarbazine, comustine, and vincristine multiagent chemotherapy. Median follow-up is 12 months. CONCLUSIONS. Occasionally, patients with AIDS and intracerebral mass lesions have primary nonlymphomatous brain tumors, an occurrence not related clearly to underlying immunoincompetence.
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25/30. Toxicity and efficacy of carboplatin and etoposide in conjunction with disruption of the blood-brain tumor barrier in the treatment of intracranial neoplasms.

    carboplatin AND etoposide have been investigated in preclinical studies and a limited toxicity study in 13 patients; these studies have established carboplatin and etoposide as a tolerable combination when administered with blood-brain barrier disruption. The studies also found a predictable dose-limiting toxicity of myelosuppression. Subsequently, a broad efficacy trial of this regimen was carried out. A total of 34 patients, ranging in age from 7 to 72 years, underwent a combination chemotherapy regimen of carboplatin (200 mg/m2 administered intra-arterially) and etoposide (200 mg/m2 administered intravenously) administered with blood-brain barrier disruption on each of 2 consecutive days every 28 days. The diagnoses included glioblastoma multiforme (n = 3), malignant astrocytoma (n = 8), malignant astrocytoma-oligodendroglioma (n = 1), primitive neuroectodermal tumor (n = 4), disseminated germ cell tumor of the central nervous system (CNS) (n = 6), CNS lymphoma (n = 7), and metastatic carcinoma (n = 5). The major toxicity observed in patients treated with multiple courses of this regimen was the expected reversible myelosuppression and an unexpected, irreversible high-frequency hearing loss. Of these 34 patients, 22 had measurable disease, and 9 radiographic responses (50% or more decrease in enhancing tumors) were observed in these patients. carboplatin and etoposide with blood-brain barrier disruption is an active regimen in the treatment of malignant astrocytomas and has shown dramatic responses in primitive neuroectodermal tumors and CNS lymphoma. Additionally, the durability of responses in patients with disseminated CNS germ cell tumors is encouraging. However, such therapy is associated with unexpected high-frequency hearing loss; even so, on the basis of the favorable responses in patients with primitive neuroectodermal tumors, germ cell tumors, and lymphomas, the study of this regimen for those tumors is being extended in a multiinstitutional trial that also includes cytoxan to further evaluate the potential enhanced drug delivery.
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26/30. Primitive neuroectodermal tumor (PNET). A case report.

    The authors present a case of relatively rare tumor of the central nervous system (CNS) in a 19-year-old female, who died 18 months after the first manifestation of meningismus, increased intracranial pressure and secondary hydrocephalus. Brain autopsy revealed abundant neoplastic infiltrations, which spread through the subarachnoid space. Neoplastic infiltrations were also present in the third ventricle and in a form of small subependymal nodules along the whole ventricular system. The microscopical examination showed that neoplasm consisted of small cells, which formed neuroblastic Homer Wright rosettes. Immunohistochemical studies (for synaptophysin, chromogranin a, GFAP, vimentin) together with morphology and localization of neoplasm suggested diagnosis of primitive neuroectodermal tumor (PNET) that spread mainly in the leptomeninges and caused obliteration of subarachnoid space.
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27/30. Primitive neuroectodermal tumor of maxilla in an adult.

    Primitive neuroectodermal tumor is primarily a central nervous system tumor. These tumors are generally manifest in infancy or early childhood. The following article reports a rare case of primitive neuroectodermal tumor in posterior maxilla in an adult. Treatment for primitive neuroectodermal tumor in extracranial sites in adults is not clearly defined in the literature. This case was treated by combined chemotherapy followed by radiotherapy, which failed to cause regression of the lesion.
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28/30. Leptomeningeal fibrosis and the delayed diagnosis of a central nervous system neoplasm (primitive neuroectodermal tumor).

    We report a unique case of histologically confirmed meningeal fibrosis in a child who had progressive ischemic neurologic symptoms before the delayed diagnosis of an intracranial primitive neuroectodermal tumor (PNET) was made > 1 year after initial presentation. This pathology has previously been described after neurosurgical procedures, subarachnoid hemorrhage, cranial irradiation, and with no known etiology, but has never been reported in association with a central nervous system neoplasm. In a 6-year-old boy with headaches of several months' duration MRI demonstrated hydrocephalus, a right cerebellopontine angle cyst, and dural enhancement. Biopsies of the thickened meninges taken when the cyst was surgically fenestrated demonstrated only fibrosis with no evidence of infection, hemorrhage, or neoplasm. In the next 6 months, the child had two acute stroke-like episodes with alternating hemiparesis that gradually improved. There were ischemic changes in the diencephalon on MRI. Repeat dural biopsies were unchanged. One year after the initial operation, a left hemiparesis recurred and MRI demonstrated multiple intracranial masses in the cerebral cortex, cerebellum, suprasellar area, and cauda equina. After surgical resection, the cortical mass was found to be a PNET. All the lesions regressed after treatment with radiation and chemotherapy. We hypothesize that the meningeal fibrosis represented a "desmoplastic" reaction to an occult PNET, similar to the fibrous proliferation with cerebellar desmoplastic medulloblastoma except for the extent of the meningeal involvement and the long undetected parenchymal tumor. The mechanism of the ischemic brain injury was most likely vascular involvement by the fibrotic process, either directly or by predisposition to vasoconstriction.
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29/30. "Polyphenotypic" tumors in the central nervous system: problems in nosology and classification.

    In recent years, there is increasing recognition of polyphenotypic high-grade malignancies in the non-central nervous system (CNS) tumor literature. Some of these tumors have been regarded as variants of primitive neuroectodermal tumor (PNET) or as extrarenal malignant rhabdoid tumors (MRTs). This report concerns two posterior fossa neoplasms, both of which displayed a "polyphenotypic" expression of neural, epithelial, myogenic, and glial markers, including synaptophysin, neurofilament, vimentin, glial fibrillary acidic protein, S-100, neuron-specific enolase, desmin, S antigen, MIC2, cytokeratin, epithelial membrane antigen, and carcinoembryonic antigen. One tumor showed complex intercellular junctions, cytoplasmic intermediate filaments, well-developed rough and smooth endoplasmic reticulum and golgi apparatus, cilia, and neurosecretory granules. The other neoplasm showed pools of glycogen, desmosomes, and tonofilaments. The histological and ultrastructural appearances were inconsistent with glioma, PNET, meningioma, ependymoma, choroid plexus carcinoma, sarcoma, germ cell tumor, and other tumors in the world health organization classification. Although the polyphenotype raises the issue that these may represent variants of MRT or the atypical teratoid-rhabdoid tumor, the morphologic findings in the two cases were very dissimilar. Our two cases underscore the problems in nosology and classification of polyphenotypic tumors of the CNS. This is particularly significant, as therapeutic protocols for PNET, MRT, and non-CNS polyphenotypic tumors are different. We review the literature on polyphenotypic tumors and reiterate the difficulties in precise classification of these complex tumors.
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30/30. Primitive neuroectodermal tumor of bone as a second malignant neoplasm in a child previously treated for acute lymphoblastic leukemia.

    PURPOSE: Although rare, second malignant neoplasms (SMNs) are a devastating consequence of successful treatment of childhood cancer. The 15-year estimated risk of developing a second malignant neoplasm after treatment of childhood acute lymphoblastic leukemia (ALL) is 2.5%. Most of these neoplasms are central nervous system tumors. The risk of secondary acute myeloid leukemia has been negligible in most treatment regimens. Here, we report the first case of a primitive neuroectodermal tumor (PNET) in a patient treated for ALL. patients AND methods: A 15.7-year-old girl developed pain in her left leg 7 years after diagnosis of low-risk ALL. Imaging studies revealed lytic lesions in her left proximal tibia and several vertebra as well as metastatic nodules in both lungs. RESULTS: Immunocytochemical and molecular analyses led to the diagnosis of PNET. The treatment of this SMN was composed of combination chemotherapy with hematopoietic growth factor support and radiotherapy to the primary lesion and affected spine. The tumor recurred 5 months after the completion of treatment, and the patient is now undergoing salvage therapy composed of chemotherapy and radiotherapy. CONCLUSIONS: To our knowledge, this is the first report of PNET as an SMN after successful treatment of ALL.
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