Abstract
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.
