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1/40. Malignant glial tumor arising from the site of a previous hamartoma/ganglioglioma: coincidence or malignant transformation?

    Gangliogliomas are generally considered benign tumors. Although more commonly found in the brain, spinal cord ganglioglioma is a well established, albeit infrequent, entity. We describe a 2-decade clinical course of a patient initially diagnosed with a thoracolumbar 'glial-neuronal hamartoma' at age 4. Seventeen years after his first operation, local recurrence was noted. Despite subsequent multiple gross total resections and adjuvant therapy, histologic features became increasingly ominous and ultimately proved fatal. This is an unusual report and histologic presentation of a resected spinal cord ganglioglioma recurring as an anaplastic ependymoma/astrocytoma and subsequently a glioblastoma. It is quite likely that the originally resected ganglioglioma was actually part of a primitive neuroectodermal tumor which had undergone extensive maturation.
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2/40. Peripheral-type primitive neuroectodermal tumor arising in the tentorium. Case report.

    The authors report the case of a peripheral primitive neuroectodermal tumor (PNET) arising in the tentorium in a 5-year-old boy who presented with frequent vomiting and mild palsy of the left abducent nerve. Following complete surgical excision of the tumor via a transpetrosal approach, the patient has thus far been disease free for 7 years. The tumor tissue was composed of small cells with uniform round nuclei and minimal identifiable cytoplasm. Homer-Wright rosettes were frequently observed. Immunohistochemical studies demonstrated a positive reaction to HBA-71, which recognizes the cell surface glycoprotein p30/32, a product of the MIC2 gene. Both the clinical and immunohistochemical characteristics of this tumor are consistent with a diagnosis of peripheral PNET, which is genetically distinct from the more common intracranial PNET.
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ranking = 9174.8037605246
keywords = rosette
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3/40. 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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ranking = 64223.626323672
keywords = rosette
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4/40. 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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ranking = 9174.8037605246
keywords = rosette
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5/40. Primitive neuroectodermal tumor of the orbit in a 5-year-old girl with microphthalmia.

    PURPOSE: To report an orbital, intraconal, primitive neuroectodermal tumor (PNET) in a 5-year-old child with microphthalmia since birth. methods: Orbitotomy was performed and a large, polycystic, retroscleral, intraconal tumor was removed and subsequent histological, immunohistochemical and electron-microscopic analyses of the excised mass were performed. RESULTS: The tumor showed characteristic features of peripheral primitive neuroectodermal tumor including pseudorosettes, positive immunohistochemical reactions for the MIC2 gene and synaptophysin and ultrastructural finding of neurosecretory granules. CONCLUSION: This case is the first reported intraconal PNET of the orbit, and the first orbital case that expresses the MIC2 gene. In spite of the aggressive malignant features of peripheral PNET, the orbital variety seems to be the least aggressive since most of the reported patients are still alive.
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ranking = 9174.8037605246
keywords = rosette
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6/40. 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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ranking = 301859.1945527
keywords = rosette formation, rosette, formation
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7/40. Cerebral primitive neuroectodermal tumor in an adult male. A case report.

    BACKGROUND: Primitive neuroectodermal tumors (PNETs) are very rare. Malignant tumors of the cerebrum in young individuals are composed predominantly of undifferentiated cells, with moderate differentiation along either neuronal or glial lines. To our knowledge, cerebral PNETs in adults are extraordinarily rare and have been reported in only 11 cases, with little cytologic documentation in the literature. The cytopathologic, immunohistochemical and ultrastructural features of cerebral PNET arising in an adult male are presented. CASE: A cystic tumor, on computed tomography and magnetic resonance imaging, arose from the left frontal lobe in a 39-year-old man and contained histopathologic features of PNET. Specimens obtained from surgery revealed the presence of an undifferentiated type of PNET with moderate neuronal and glial differentiation and mild characteristic findings of peripheral PNET. The cytologic and histologic specimens showed evidence of a scattered pattern of blastic and undifferentiated tumor cells and a neural arrangement with Homer-Wright-like rosettes. Immunohistochemically, the tumor cells were glial fibrillary acidic protein, neuron-specific enolase, synaptophysin and CD-99 positive and epithelial membrane antigen, S-100 protein and vimentin negative. Ultrastructurally, neither microtubular structures nor intermediate filaments, except neurosecretory granules, were found in the tumor cells. CONCLUSION: Both immunohistochemical and ultrastructural studies on cytologic and histologic slides were important for the diagnosis of PNET because of establishing not only undifferentiated tumor cells but also neural and glial differentiation.
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ranking = 9174.8037605246
keywords = rosette
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8/40. Primitive neuroectodermal tumor of the lung.

    Primitive neuroectodermal tumors occur most frequently in bone and soft tissue but have been reported in other locations. Primary lung primitive neuroectodermal tumors without pleural or chest wall involvement are extremely rare. We present a case with immunohistochemical and ultrastructural studies and follow-up of the patient. An 18-year-old man presented with hemoptysis. Chest radiographs revealed a right middle lobe mass, and bronchoscopy showed an endobronchial tumor. The lesion was resected by middle lobectomy. After 2 years, a local recurrence was treated by pneumonectomy. The patient died after surgery. Histologically, the tumor was composed of uniform cells with round nuclei and scanty cytoplasm arranged in cohesive lobules with occasional rosette formation. Immunohistochemically, the tumor was positive for vimentin, CD99, neuron-specific enolase, and neurofilaments. Ultrastructural study revealed neurosecretory granules and cytoplasmic processes. Our case shows the value of immunohistochemistry and electron microscopy in the diagnosis of primitive neuroectodermal tumors in unusual locations.
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ranking = 301859.1945527
keywords = rosette formation, rosette, formation
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9/40. PNET-like features of synovial sarcoma of the lung: a pitfall in the cytologic diagnosis of soft-tissue tumors.

    Fine-needle aspiration (FNA) cytology of soft-tissue tumors is evolving. As more experience is gained, we are becoming aware of potential pitfalls. We describe 2 cases of synovial sarcoma of the lung, primary and metastatic, in patients who had FNA biopsy performed on a lung mass. The cytologic smears showed extremely cellular groups of malignant small round cells, intersected by small blood vessels, with numerous loose single cells, in a background of macrophages and mature lymphocytes. The tumors displayed monomorphic cells forming rosettes and displaying occasional mitoses. A diagnosis of neuroendocrine tumor/primitive neuroepithelial tumor (PNET) was suspected. Furthermore, this suspicion was supported by immunohistochemical stains, which showed positivity for a neuroendocrine marker, Leu 7 (case 1), and for a neural marker, CD 99 (O 13 or HBA 71) (both cases); and negativity for cytokeratins (case 1). The resection specimen of case 1 had mostly tightly packed small round cells, with occasional rosettes, similar to the FNA biopsy, and focal areas composed of spindle cells, organized in a focal fibrosarcoma-like and hemangiopericytoma-like pattern. A balanced translocation between chromosomes X and 18, demonstrated by both karyotyping and fluorescent in situ hybridization (FISH), enabled us to make a diagnosis of synovial sarcoma, which was histologically classified as poorly differentiated. Case 2 was a metastatic biphasic synovial sarcoma of the arm, with a prominent epithelial component. Synovial sarcoma, when composed mainly of small round cells on cytologic smears, is a great mimicker of neuroendocrine/PNET tumors, with light microscopic and immunohistochemical overlap. awareness of this potential pitfall may aid in preventing a misdiagnosis. Its recognition is of major concern, especially for the poorly differentiated variant, because it is associated with a worse prognosis.
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ranking = 18349.607521049
keywords = rosette
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10/40. Metastatic primitive neuroectodermal tumor of the kidney in adults.

    OBJECTIVE: Primitive neuroectodermal tumors (PNET) of the kidney are rare and highly aggressive malignancies. The purpose of our study was to present information about the management of patients with metastatic disease. methods: The records of 2 patients (30-year-old female and 32-year-old male) with metastatic PNET of the kidney were reviewed and our data compared with the literature. RESULTS: Neither clinical evaluation nor radiological methods allowed to distinguish PNET from renal cell carcinoma. immunohistochemistry revealed strong positivity for CD99 in tumor 1 and weak positivity for NSE and vimentin in both tumors. In tumor 2, EWS/FLI1 translocation was detected by RT-PCR. Patient 1 underwent nephrectomy, seven cycles of polychemotherapy, two cycles of high-dose chemotherapy, autologous bone marrow rescue, radiotherapy of suspicious skeletal foci and is without evidence of recurrent disease 28 months after therapy. Patient 2 underwent six cycles of polychemotherapy, nephrectomy, high-dose chemotherapy with cyclophosphamide and abdominal radiotherapy. Because of relapse high-dose chemotherapy with stem cell rescue was not performed. He underwent three further cycles of polychemotherapy and died one year after diagnosis due to cerebral metastasis. CONCLUSIONS: The diagnosis of renal PNET must be considered in young patients with renal neoplasm, particularly those with advanced disease at presentation. Achieving exact diagnosis has important clinical consequences because polychemotherapy and high-dose chemotherapy may lead to dramatic tumor reduction or even complete remission.
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