Keishi Horiguchi

Gunma University, Maebashi-shi, Gunma-ken, Japan

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Publications (4)12.52 Total impact

  • Atsushi Sasaki, Keishi Horiguchi, Yoichi Nakazato
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    ABSTRACT: We report a case of pineal parenchymal tumor in a 33-year-old man incidentally detected by radiological examination. The MRI showed an unhomogeneously enhanced, small tumor (approximately 1 cm in size) in the pineal region. A tumor specimen was obtained at endoscopic biopsy. Routine histology showed a highly cellular tumor characterized by a predominance of small cells showing high nuclear : cytoplasmic ratio and moderate nuclear atypia, pleomorphism including giant cells and an absence of pineocytomatous rosettes. Mitotic figures were rare (approximately 1 per 10 high-power fields). Tumor necrosis was not evident. Immunohistochemically, the neoplastic cells showed positivity for neural markers (neurofilament protein, synaptophysin) and pinealocyte-associated antibodies (PP1, PP5, PP6), but not for glial fibrillary acidic protein or S-100. The MIB-1 labeling index was relatively high (6.3%). Ultrastructurally, there was some evidence of pinealocytic differentiation, such as vesicle-crowned rodlets (synaptic ribbons) and paired twisted filaments in neoplastic cells. Thus, the tumor was confirmed as a pineal parenchymal tumor of intermediate differentiation by histology, immunohistochemistry and electron microscopy. This case indicates that marked cytologic pleomorphism can occur in pineal parenchymal tumors of intermediate differentiation.
    Neuropathology 07/2006; 26(3):212-7. · 1.91 Impact Factor
  • Keishi Horiguchi, Takashi Fujii, Yoichi Nakazato
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    ABSTRACT: We describe a new case of isolated Langerhans cell histiocytosis (LCH) of the hypothalamus. A 53-year-old female patient presented with polydipsia, headache, anorexia, and fatigue. Neurological imaging revealed a mass projecting from the hypothalamus into the third ventricle. Gross total removal of the tumor was performed. Light microscopy showed LCH, and immunohistochemical studies revealed S-100 and CD1a immunoreactivity in the Langerhans cells. Although the most common CNS site for LCH is the hypothalamus, isolated hypothalamic LCH, confirmed by biopsy, is very rare. The residual mass appeared to remit spontaneously 3.5 years after surgery, with regrowth 3 years later.
    Brain Tumor Pathology 02/2004; 21(2):97-101. · 1.58 Impact Factor
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    ABSTRACT: The human Ras association domain family 1A (RASSF1A) gene, recently isolated from the lung and breast tumor suppressor locus 3p21.3, is highly methylated in primary lung, breast, nasopharyngeal and other tumors, and re-expression of RASSF1A suppresses the growth of several types of cancer cells. Epigenetic inactivation of RASSF1A by promoter hypermethylation is also important in the development of several human cancers. The methylation status of the promoter region of RASSF1A was analysed in primary brain tumors and glioma cell lines by methylation-specific polymerase chain reaction. In primary brain tumors, 25 of 46 (54.3%) gliomas and five of five (100%) medulloblastomas showed RASSF1A methylation. In benign tumors, only one of 10 (10%) schwannomas and two of 12 (16.7%) meningiomas showed RASSF1A methylation. The RASSF1A promoter region was methylated in all four glioma cell lines. RASSF1A was re-expressed in all methylated cell lines after treatment with the demethylating agent 5-aza-2'-deoxycytidine. Methylation of the promoter CpG islands of the RASSF1A may play an important role in the pathogenesis of glioma and medulloblastoma.
    Oncogene 11/2003; 22(49):7862-5. · 7.36 Impact Factor
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    ABSTRACT: Precise determination of the spinal level of a cerebrospinal fluid leak is important in the diagnosis and treatment of spontaneous intracranial hypotension. The authors report two cases of SIH in which a cerebrospinal fluid leak was demonstrated by three-dimensional computed tomographic (3D-CT) myelography. By overlaying 3D-CT images of contrast-enhanced CSF and the spine, the point of leakage was clearly depicted in the three-dimensional spinal structure, which assisted targeted epidural blood patch under the guidance of fluoroscopy. Although associated chronic subdural hematoma had to be treated by burr hole drainage, the patients' postural headaches subsided after treatment. Clear CSF images in relation to vertebral bones are obtainable with 3D-CT myelography, rendering this modality very useful for the diagnosis and treatment of spontaneous intracranial hypotension.
    Surgical Neurology 01/2002; 58(3-4):280-4; discussion 284-5. · 1.67 Impact Factor