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1/51. Peripheral primitive neuroectodermal tumor of the parotid gland region: report of a case with fine-needle aspiration findings.

    A case of peripheral primitive neuroectodermal tumor of the parotid gland region in a 38-yr-old woman is reported. She had a 1-yr history of a large, firm, and slightly tender left parotid-region mass. CT scan showed an invasive tumor involving the parotid gland, mandible, infratemporal fossa, and parapharyngeal space. Fine-needle aspiration cytology of the mass showed a highly cellular, poorly cohesive smear pattern exhibiting small cuboidal cells, with fibrillary cytoplasm forming occasional rosette-like structures. Numerous intact single cells with fragile cytoplasm, finely granular chromatin, and inconspicuous nucleoli were present together with free-lying nuclei in the background. Histologic, immunohistochemical, and ultrastructural findings confirmed the diagnosis. Diagn. Cytopathol. 2000;22:161-166. Published 2000 Wiley-Liss, Inc.
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ranking = 1
keywords = rosette
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2/51. Peripheral primitive neuroectodermal tumor of the small bowel mesentery: a case showing perforation at onset.

    A case of peripheral primitive neuroectodermal tumor of the small bowel mesentery with an uncommon clinical onset is reported. A 40-year-old man was admitted to hospital because of acute severe abdominal pain. Chest X-ray revealed a free air sign beneath the diaphragm. At emergency surgery a mass measuring 11.0 x 8.0 cm with perforation was located in the jejunal mesenteric region. Histologically the resected lesion consisted of sheets of undifferentiated small round cells forming abortive Homer Wright rosettes. Some spindle-shaped cells showed perivascular pseudorosettes. Immunohistochemical study revealed that the tumor cells expressed positivity against CD99 (MIC2), neuron-specific enolase, synaptophysin and vimentin. To the authors' knowledge this is the first documentation of peripheral primitive neuroectodermal tumor of the small bowel mesentery with perforation at onset.
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keywords = rosette
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3/51. Ewing's sarcoma/peripheral primitive neuroectodermal tumor (pPNET) arising in the omentum as a multilocular cyst with intracystic hemorrhage.

    A rare case of Ewing's sarcoma/peripheral primitive neuroectodermal tumor arising in the greater omentum in a 41-year-old man is reported. The patient presented with a hemorrhagic mesenteric cyst that was disclosed by the results of an abdominal echogram, a computed tomography scan, and magnetic resonance imaging. A laparotomy showed a multilocular cyst with intra-cystic hemorrhage. Histologically, the tumor wall consisted of sheets of small round cells separated by thick desmoplastic stroma. Rosette formations or ribbon-like cell arrangements were absent. Further pathological examination revealed that the membrane of the tumor cells was positive for MIC-2, and negative for epithelial membrane antigen, cytokeratin, and desmin, which are usually positive in intra-abdominal desmoplastic small round-cell tumors. An EWS/FLI1 fused transcript was detected by reverse transcription-polymerase chain reaction. These findings confirmed the diagnosis of Ewing's sarcoma/peripheral primitive neuroectodermal tumor. The patient died of tumor recurrence 4 months after his first admission. The autopsied tumor tissue exhibited neural differentiation in certain regions. To our knowledge, this is the first case to be reported of Ewing's sarcoma/peripheral primitive neuroectodermal tumor arising in the omentum with unique pathological features and the occurrence of partial neural differentiation during the clinical course. This case pointed out to us, as gastroenterologists, that only thorough examination confirms a definitive diagnosis of small round-cell tumor of the abdomen, it also shows that Ewing's sarcoma/peripheral primitive neuroectodermal tumor should be included in the differential diagnosis of cystic lesions in the omentum.
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ranking = 0.00012006166080932
keywords = formation
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4/51. Peripheral primitive neuroectodermal tumor of the vulva: report of a case with imprint cytology.

    BACKGROUND: Peripheral primitive neuroectodermal tumor (PNET) of the vulva is an extremely rare disease, and, to our knowledge, only two cases have been previously reported. CASE: A 45-year-old woman presented with a mass in the right labium major. Three years after removal of the tumor, she noticed a new lesion in the same place and underwent a partial vulvectomy. The imprint cytology of the recurrent tumor showed a monomorphic appearance, composed of small round cells with scant cytoplasm against a hemorrhagic background. These tumor cells were loosely connective, but rosettelike structures were observed focally. On pathologic examination, the neoplasm was composed of small round tumor cells showing sinusoidal, diffuse or micropapillary growth. Immunohistochemically, the neoplastic cells stained positively for neuron-specific enolase, vimentin and HBA 71 and negatively for cytokeratin, HBA 45 and muscle-specific actin. The morphologic characteristics of the disease were well expressed in the imprint cytology, and this influenced the selection of immunohistochemical studies. CONCLUSION: Cytologic examination for vulvar tumors, even imprint cytology, can be a useful tool in obtaining an accurate pathologic diagnosis of a rare disease, such as peripheral PNET.
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5/51. cytodiagnosis of retroperitoneal primitive neuroectodermal tumour (PNET)--a case report.

    A rare case of Retroperitoneal Primitive Neuro Ectodermal Tumour (PNET) in thirty years old female is presented. Fine needle aspiration cytology (FNAC) characterised by small round cells with scanty cytoplasm, poorly to well formed rosettes with neurofibrillary background; whereas periodic acid-schiff (PAS) rarely react with Primitive Neuro Ectodermal Tumour (PNET), prompted the diagnosis of PNET at cytology itself. Cytological appearances of PNET have been reviewed and the various differential diagnoses are discussed.
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6/51. Primitive neuroectodermal tumor of the transverse colonic mesentery defined by the presence of EWS-FLI1 chimeric mRNA in a Japanese woman.

    We report a case of primitive neuroectodermal tumor (PNET) arising in the transverse colonic mesentery. A 24-year-old Japanese woman was admitted to Kagoshima City Hospital with complaints of abdominal pain and sensations of abdominal fullness of 5 months' duration. On palpation, a mass the size of an infant's head was noted in the right flank. Abdominal computed tomography (CT) and ultrasonography showed a huge mass that consisted of multiple cystic components. On arteriography, a slight tumor stain appeared, with stretched and displaced tributaries of the right colic and middle colic arteries. barium swallow examination demonstrated that the ascending colon was shifted to the right and small intestine to the left. We performed an en-bloc resection of the tumor in the transverse colonic mesentery, including the ascending colon, proximal jejunum (20 cm in length), and greater omentum. The resected tumor was 12 x 10 x 7 cm in size, 590g in weight, elastic soft in consistency, and multicystic. Histologically, the specimens showed a sheet-like proliferation of spindle-to-polygonal cells, and focally, the tumor formed rosette structures. Immunohistochemically, the tumor cells were positive for neuron-specific enolase (NSE) and mic-2. EWS-FLI1 chimeric mRNA was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Based on the above findings, we finally diagnosed the tumor as PNET of the colonic mesentery. There has been no recurrence for 20 months after operation. PNET arising in the mesentery is very rare, and we distinguished PNET from other tumors by immunohistochemical examination and by demonstration of the presence of EWS-FLI1 chimeric mRNA in the tumor.
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keywords = rosette
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7/51. Peripheral primitive neuroectodermal tumor presenting in the retroperitoneum: a case report with immunohistochemical study.

    It is now believed that malignant peripheral primitive neuroectodermal tumor (PNET) form a distinct tumor entity from other malignant small round cell tumors exhibiting neuroectodermal differentiation by morphologic, immunohistochemical or electron microscopic analyses. A 17-year-old Ethiopian boy was found to have a big upper extra osseous retroperitoneal tumor mass not associated with peripheral nerve that had infiltrated the body of the pancreas. Histologic sections from excised biopsy showed neoplastic cells with a high nuclear-cytoplasmic ratio and had an indistinct cytoplasm with numerous Homer-Wright rosettes. Immunohistochemically, isolated tumor cells and the centre of rosettes disclosed strong positivity to neural markers, synaptophysin and chromogranin. To the best of our knowledge, this case report represents the first patient described in ethiopia.
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ranking = 2
keywords = rosette
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8/51. Primitive neuroectodermal tumours of the uterus: a case report with cytological correlation and review of the literature.

    A case of primitive neuroectodermal tumour (PNET) co-existing with endometrial adenocarcinoma of the uterus is reported in a 48-year-old female. Histologically, the neoplastic cells formed neuroectodermal rosettes and displayed ependymal differentiation. Focal positive immunohistochemical staining for synaptophysin, chromogranin a, CD57 and cytokeratins was noted. Merging imperceptibly with the neuroectodermal component were areas of endometrial adenocarcinoma and, to the best of our knowledge, this report represents the second case of a uterine PNET with an admixed mullerian component. The patient was disease-free 6 months following surgical resection of the tumour. The literature on this uncommon entity is critically reviewed and the histogenesis, differential diagnoses and cytomorphological features of PNET are also discussed.
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keywords = rosette
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9/51. neuroblastoma-like schwannoma: a case report and review of the literature.

    We report a case of schwannoma (neurilemmoma) predominantly composed of small cells arranged in rosettes around central collagenous cores and discuss the differential diagnosis of this unusual variant. Schwannoma with giant rosettes, previously designated as neuroblastoma-like schwannoma by Goldblum et al., must be differentiated from neuroblastoma, peripheral neuroectodermal tumors, and malignant change in a schwannoma.
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ranking = 2
keywords = rosette
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10/51. Primitive neuroectodermal tumor of the kidney. A report of two cases diagnosed by fine needle aspiration cytology.

    BACKGROUND: Primitive neurocetodermal tumors (PNETs) constitute a family of neoplasms of presumed neuroectrodermal origin most often presenting as bone or soft tissue masses. There are very few reported cases of PNET of the kidney and none diagnosed by fine needle aspiration cytology (FNAC), to the best of our knowledge, in the world literature. We present two cases of renal PNET diagnosed on cytology. CASES: Two patients with renal masses were diagnosed as having PNET on FNAC. Cytologically the tumors showed a dispersed population of malignant small round cells with focal rosette formation and perivascular arrangement of tumor cells. immunohistochemistry on the cell blocks in both cases showed strong membrane positivity for CD99 (MIC2). Cytogenetic studies in both cases showed the characteristic t(11;22)(q24;q12) translocation, with additional chromosomal abnormalities in case 2. CONCLUSION: PNET of the kidney is a distinct entity and can be diagnosed on fine needle aspiration smears and confirmed with immunohistochemistry and cytogenetic studies. A diagnosis of PNET must be included in the differential diagnosis of renal masses in adolescents and young adults.
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ranking = 1.0001200616608
keywords = rosette, formation
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