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1/30. Pediatric neuroblastic brain tumors containing abundant neuropil and true rosettes.

    We have encountered a series of seven unusual neuroblastic pediatric central nervous system (CNS) neoplasms with a unique constellation of histologic, immunohistochemical, and ultrastructural features. The tumors presented in five girls and two boys, ages 1 to 3 years. In six cases the lesions involved the frontoparietal region, in one case the tectal plate. The tumors consisted of small to medium-sized, round to oval, hyperchromatic cells with poorly defined cytoplasmic borders. cells were found in clusters and cords set in a paucicellular fibrillar neuropil matrix. Distinctive, virtually anuclear regions of neuropil were scattered throughout the lesions. True rosettes with well-formed central lumens often filled with granular debris were present, along with perivascular pseudorosettes and occasional Homer-Wright rosettes. Mitoses and apoptosis were frequent, but large regions of confluent necrosis were absent. Immunohistochemically, the neuropil-like areas as well as the perinuclear cytoplasm of many embryonal tumor cells were positive for synaptophysin and neurofilament protein. Ultrastructurally, the tumor cells showed microtubule-containing neuronal processes, some with neurosecretory granules. While the lesions were largely glial fibrillary acidic protein (GFAP) negative, there was focal GFAP positivity consistent with divergent differentiation in one case. The clinical outcome was poor, with five patients dead from their disease 5 to 14 months after initial presentation and one patient with recurrent disease 7 months after resection and chemotherapy. The final patient is alive without recurrent disease 30 months after initial presentation. These lesions present distinctive histological features within the group of primitive neuroectodermal tumors.
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2/30. Primitive neuroectodermal tumor of the uterus. A case report.

    BACKGROUND: Primitive neuroectodermal tumor (PNET) is a rare tumor derived from fetal neuroectodermal cells. These tumors occur in the central nervous system and in peripheral locations. Histologic diagnosis is the standard since most of these tumors are detected at an advanced stage. CASE: A 17-year-old female presented with persistent vaginal bleeding. physical examination revealed a 4-cm, hard, barrel-shaped cervix. A cervicovaginal smear was obtained. The specimen was hypercellular, with small to medium-sized, round, malignant cells. A diagnosis of PNET was made from the histologic sections of the surgical specimen. CONCLUSION: When numerous small round cells in a diffuse pattern are seen on a Pap smear, the differential diagnosis is long and difficult. However, with careful evaluation of the cytologic features, a few reasonable differential diagnoses can be reached. Furthermore, with liquid-based Pap smears, material is available for immunohistochemical staining to narrow the range even more. Using all resources, including a good clinical history, a cytopathologist can give the clinician an early diagnosis for intervention and treatment.
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3/30. Primitive neuroectodermal tumor of the pancreas. An extremely rare tumor. Case report and review of the literature.

    Peripheral primitive neuroectodermal tumor (PPNET) is a malignant neoplasm of the peripheral nervous system and soft tissues. Representing the fourth case published we herein report a PPNET arising in the pancreas of a six year old girl. She presented with severe anemia due to ulcerative tumor growth and hemorrhage into the duodenum. From the first biopsy pancreatoblastoma was considered as histological diagnosis. Therefore pancreato-duodenectomy was successfully performed. Immunohistochemically, the tumor cells were positive for cytokeratines and several neuronal markers. Due to focal membranous staining for MIC-2 gene product and rosettes in one lymph node metastasis the diagnosis had to be altered into PPNET. This was confirmed by cytogenetic analysis. We conclude that the interpretation of histologic sample excisions from pediatric pancreatic neoplasms may be difficult and that PPNET should be included in the differential diagnosis.
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4/30. Primary primitive neuroectodermal tumor of the kidney.

    Primitive neuroectodermal tumor (PNET) is a small round cell sarcoma that mainly develops in the central nervous system and soft tissues of childhood; however recently, primary occurrence of this tumor in the kidney has been reported. We experienced one case of PNET primarily arose in the kidney without metastasis. The patient was a 28-year-old man whose chief complaint was abdominal pain, especially on exercise. On computed tomography scan and magnetic resonance imaging, a solid lesion was found in the left kidney, and a left nephrectomy was performed based on the diagnosis of a tumor in the left kidney. The tumor was within the parenchyma of lower end of left kidney protruding into the abdominal cavity. Histologically, diffuse proliferation of primitive small round cells with rosette formation was found. Immunohistochemically, MIC2 gene product, neuron-specific enolase and S-100 protein were positive. No metastasis to the regional lymph nodes was found. From these observations, the tumor was diagnosed as PNET primarily arising in the left kidney. Although chromosome analysis was not performed, EWS-FLI1 chimera gene was identified by reverse transcriptase-polymerase chain reaction on the freshly frozen specimen and fluorescence in situ hybridization on paraffin sections.
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5/30. Primitive neuroectodermal tumor of cerebrum with adipose tissue.

    Primitive neuroectodermal tumors (PNETs) of the central nervous system are uncommon embryonal neoplasms, rarely occurring in adults. Differentiation into specific mesenchymal tissues, such as cartilage, bone, skeletal muscle, smooth muscle, or adipose tissue, is rare. We report a case of a 51-year-old woman with a PNET of cerebrum that showed extensive mature adipose tissue differentiation. This is the second case, to our knowledge, of PNET of cerebrum with adipose tissue elements that has been described.
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6/30. Cytogenetic and histopathologic studies of congenital supratentorial primitive neuroectodermal tumors: a case report.

    Primitive neuroectodermal tumors (PNET) represent about 25% of primary central nervous system tumors in childhood, but congenital PNETs are rare. Cytogenetic studies and studies on molecular pathology have identified several genetic alterations in medulloblastoma, but molecular investigations on supratentorial PNETs are infrequent. We present a male newborn with a large congenital PNET of the right cerebral hemisphere and the molecular analysis of the tumor. Tumor tissue was investigated by routine histology and immunohistochemistry. fluorescence in-situ hybridization was carried out on native tumor tissue to investigate deletions on chromosome 17p and to analyze c-Myc or N-Myc amplifications. Histologic examination revealed a primitive neuroectodermal tumor with massive extension covering almost the entire right hemisphere. Genetic analysis of the native tumor tissue of our patient excluded a deletion of chromosome 17p. An amplification of the c-Myc or N-Myc oncogene was absent using fluorescence in-situ hybridization. Despite unremarkable genetic analysis in our case prognosis was poor, suggesting that there are additional, yet unknown constitutional genetic aberrations in the pathogenesis of congenital supratentorial PNET.
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7/30. Primary Ewing's sarcoma/peripheral primitive neuroectodermal tumor at the vertex of the skull with elevated serum carcinoembryonic antigen: case report.

    A primary Ewing's sarcoma arising in the skull is relatively rare. Although a small number of case reports noted elevated carcinoembryonic antigen (CEA) in patients with primary central nervous system (CNS) neoplasms, there is no report of Ewing's sarcoma/peripheral primitive neuroectodermal tumor (PNET) with elevated serum levels of CEA. A 7-year-old boy who had episodes of headache and vomiting had noticed a solid mass in the vertex of the head. Imaging studies revealed a large intra- and extracranial tumor at the vertex of the skull. Hematological examination demonstrated high serum levels of CEA: 91.09 ng/ml. The patient initially underwent an embolization of the bilateral middle meningeal arteries with Gelfoam particles. One week later, the patient was operated on and a subtotal resection of the tumor was performed. On histopathological and molecular genetic examination, the tumor was diagnosed as a Ewing's sarcoma/peripheral PNET. Immunohistochemical study showed strongly positive staining for CEA in the tumor cells. The serum level of CEA was normalized at 0.83 ng/ml after the tumor was removed and the boy underwent radiotherapy and 3 courses of chemotherapy. This is the first reported case of a primary Ewing's sarcoma/peripheral PNET at the vertex of the skull with elevated serum CEA.
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8/30. Sellar and suprasellar medulloepithelioma.

    Medulloepithelioma is a rare tumour with a very poor prognosis. The most frequent site in the central nervous system is the cerebral hemispheres. Appearances on MRI are very variable, possibly reflecting the divergent forms of differentiation seen at histological examination. We report a rare case of sellar and suprasellar medulloepithelioma in a 2-year-old boy and discuss the imaging, differential diagnosis and pathologic findings.
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9/30. Foreign body reaction to hemostatic materials mimicking recurrent brain tumor. Report of three cases.

    Chemical agents routinely used in neurosurgery to achieve intraoperative hemostasis can cause a foreign body reaction, which appears on magnetic resonance (MR) images to be indistinguishable from recurrent tumor. Clinical and/or imaging evidence of progression of disease early after surgical resection or during aggressive treatment may actually be distinct features of granuloma in these circumstances. A series of three cases was retrospectively analyzed for clinical, imaging, surgical, and pathological findings, and the consequences they held for further disease management. All patients were boys (3, 3, and 6 years of age, respectively) and all harbored primitive neuroectodermal tumors. Two tumors were located in the posterior fossa and one was located in the right parietal lobe. Two boys exhibited clinical symptoms, which were unexpected under the circumstances and prompted new imaging studies. One patient was asymptomatic and imaging was performed at planned routine time intervals. The MR images revealed circumscribed, streaky enhancement in the resection cavity that was suggestive of recurrent disease. This occurred 2 to 7 months after the first surgery. At repeated surgery, the resected material had the macroscopic appearance of gelatin sponge in one case and firm scar tissue in the other cases. Histological analysis revealed foreign body granulomas in the resected material, with Gelfoam or Surgicel as the underlying cause. No recurrent tumor was found and the second surgery resulted in imaging-confirmed complete resection in all three patients. Because recurrent disease was absent, the patients continued to participate in their original treatment protocols. All patients remain free from disease 34, 32, and 19 months after the first operation, respectively. During or after treatment for a central nervous system neoplasm, if unexpected clinical or imaging evidence of recurrence is found, a second-look operation may be necessary to determine the true nature of the findings. If the resection yields recurrent tumor, additional appropriate oncological treatment is warranted, but if a foreign body reaction is found, potentially harmful therapy can be withheld or postponed.
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10/30. brain specific human genes, NELL1 and NELL2, are predominantly expressed in neuroblastoma and other embryonal neuroepithelial tumors.

    NELL1 and NELL2 encode cysteine-rich amino acid sequences including six epidermal growth factor-like motifs, which contain signal peptides at the N-terminals. The deduced amino acid sequences of both genes are 55% identical and their cysteine stretch structures are conserved. NELL1 is expressed in the brain and kidney, whereas NELL2 is expressed specifically in the brain. The cell lineage expressing NELLs in the nervous system was investigated in established cell lines and central nervous system tumor tissues obtained from patients by Northern blot and reverse transcriptase-polymerase chain reaction analyses. NELL1 and NELL2 were predominantly expressed in neuroblastoma cell lines and little expressed in glioblastoma cell lines. NELL1 and NELL2 were also expressed in central neurocytoma, medulloblastoma, and some astrocytic tumors. Immunohistochemical analysis revealed that NELL2 protein was localized in the cytoplasm of neurons. These results suggest that NELL2 is predominantly expressed in the neuronal cell lineage in the human nervous system. NELL1 is expressed mainly in tumors in the neuronal cell lineage.
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