Although pineal region tumors （PRTs） are rare overall, PRTs exhibit various types of histology, including germ cell tumors （GCTs）, pineal parenchymal tumors （PPTs）, gliomas, meningiomas, pineal cyst, and thepapillary tumor of the pineal region.GCTs are most frequent, and germinomas account for approximately 47％. After GCTs, PPTs are most common. In this article, the pathological characteristics and points of differential diagnosis in PRTs are reviewed to help better understanding of the tumor and communication between the neurosurgeons and the neuropathologists.

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Among central nervous system （CNS） tumors, embryonal tumors are classified into three tumor entities: medulloblastoma, CNS primitive neuroectodermal tumor （PNET）, and atypical teratoid/rhabdoid tumor （AT/RT）. Differential diagnosis among these three tumor entities is important; in particular, the diagnosis of AT/RT should be a top priority because tumor prognosis is dismal and the therapy strategy for AT/RT is different from other tumors. INI1 immunostaining is useful in diagnosing AT/RT, but cannot always resolve the problems in the pathological diagnosis of AT/RT and related tumors. Taking into account the histological, immunohistochemistry, and clinical findings, we should synthetically diagnose these tumors. Medulloblastoma and CNS PNET should be distinguished from anaplastic ependymoma, glioblastoma, central/extraventricular neurocytoma, immature teratoma, malignant lymphoma, myeloid sarcoma, and Ewing sarcoma/peripheral PNET. Differential diagnosis of these tumors can be performed by the intimate cytological and architectural features and the expression pattern in the panel of immunohistochemical markers. In addition, the detection of amplification of 19q13.42 is a useful tool in differentiating ependymoblastoma/embryonal tumors with abundant neuropil and true rosettes and medulloepithelioma from other tumors.

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Central nervous system primitive neuroectodernal tumors （cPNETs） are an entity of embryonal tumors mailny ocurring in children. They are quite rare, but heterogeneous, including NOS PNET, neuroblastoma, ganglioneuroblastoma, medulloepithlioma, and ependymoblastoma in WHO 2007. Recently, major advances in the diagnosis and treatment have led to improved outcomes of them.This manuscript reviews and summaries the pathological and clinical features of cPNETs.

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Recent advent in molecular pathological investigations has elucidated the cytodifferentiation of pituitary cells, and lots of transcriptional factors are found to regulate the cytodifferentiation of pituitary cells. The scheme of cytodifferentiation is closely related to the pathogenesis of pituitary adenomas. Meanwhile, the role of hypothamic hormones in the development of pituitary adenomas has recently attracted the attention of investigators. Growth hormone-releasing hormone expression in somatotroph adenomas, and corticotropin-releasing hormone expression in corticotroph adenomas have been demonstrated. Such evidence indicates that endogenous expression of hypothalamic hormones and their receptors in human pituitary adenoma cells has ample significance in autocrine or paracrine regulation of pituitary hormone production and tumor extension by hypothalamic hormone produced by adenoma cells.The recent progress in surgical modalities of pituitary adenomas has provided several alternatives; transsphenoidal surgery v.s. transcranial surgery, sublabial approach v.s. endonasal approach, and microsurgery v.s. endoscopic surgery. Medical treatment of pituitary adenomas are also in progress. Frequently used dopamine agonist, cabergoline, is very effective for prolactin producing adenoma. Long-acting octreotide, lanreotide and pegvisomant are now available for growth hormone producing adenoma. Cabergoline is also used for growth hormone producing adenoma. Temozolomide has recently been used for atypical adenomas or pituitary carcinomas. Adult growth hormone deficiency sometimes occurs in postoperative patients with pituitary adenomas. Growth hormone replacement is recommended to maintain the quality of life of these patients.

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Gliosarcoma is a malignant glial neoplasm which consists of both gliomatous and sarcomatous components. It arises commonly in the cerebral hemispheres of middle-aged individuals and shows a characteristic “biphasic” histopathological appearance. The gliomatous component usually shows the features similar to those of glioblastoma, and the sarcomatous component exhibits an appearance of spindle cell sarcoma resembling fibrosarcoma. Cytogenetic studies have revealed that gliosarcoma is a variant of primary （de novo） glioblastoma. The histogenesis of gliosarcoma has been controversial for a long time, but it has been established in recent years that the sarcomatous component of gliosarcoma is derived from the “heterodifferentiation” （or “neometaplasia”） of glioblastoma cells. It has also been presumed that the “epithelial-mesenchymal transition” phenomenon plays an important role in the histogenesis of gliosarcoma.

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Since the molecular-based classification of gliomas has been a trend in recent years, pathological diagnoses are required to balance that trend. In oligodendrogliomas, the combination of a classic morphology with positive mutant IDH1 and negative p53 findings on immunohistochemistry is highly correlated with the genetic signature of the 1p/19q co-deletion and IDH mutation. Oligodendrogliomas with a non-classic histology often lack this genetic signature. Oligoastrocytomas exhibit a non-classic histology, even if they have the co-deletion, suggesting that they may be distinct from classic oligodendrogliomas. In high-grade gliomas, the identification of an oligodendroglioma component is controversial, as these lesions always display non-classic features. For patients with such lesions, genetic testing is mandatory. Non-deleted, non-classicoligodendrogliomas are, however, not always astrocytomas, and an effort to identify novel genetic markers is required. The future classification of gliomas should take into account both phenotypes and genotypes; however, it is premature to switch from a morphologic diagnosis to genetic testing, as the latter is not universally available. This review summarizes the current knowledge of pathological features of oligodendroglioma.

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Dokkyo Medical University was established in 1973, and cerebrated 40 years anniversary last year. Department of Neurologic Surgery was founded by Dr. Masakatsu Nagai, one of the establishing members of Japanese Society of Neuro-Oncology. Dr. Phyo Kim is the current chairman, who also serves as the president of Japanese Society of Spinal Surgery. Dokkyo Neurologic Surgery is one of the largest neurosurgical practice in Japan, performing 850~900 surgical cases per year. Brain tumor surgeries are around 140-150 each year, about half of which are malignant cases requiring adjuvant therapy to follow. 120-150 cases of Gamma Knife are also performed. The institution has Gamma Knife, cyclotron-equipped PET Center, which allow state-of-the-art management for all intracranial neoplasms. In addition, very active Pediatric Oncology Group is in close relationship to work with on pediatric cases. Routinely running a clinical molecular diagnosis unit, we offer best surgical expertise, accurate diagnosis, and best treatment for patients with brain tumor. Located at the geographical center of North Kanto Area in Japan, Dokkyo Medical University covers 2.5 million population, and function as the final referral hospital in this lesion.

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