Participation of perineurial cells in peripheral nerve sheath tumors and FISH ananysis of their chromosomal abnormalities

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To clarify the role of perineurial cells in peripheral nerve sheath tumors (PNST), the following three studies were carried out. A new entity, malignant perineurial cell tumor, was proposed ; scierosing perineurioma was pathologically characterized ; and the presence of perineurial cells was immunohistochemically revealed in neurofibromas.1.Perineurial malignant peripheral nerve sheath tumor (MPNST)To determine the clinicopathologic, immunohistochemical and ultrastructural characteristics of perineurial MPNST, 121 MPNST were examined ; 23 spindle cell tumors with long processes disposed in whorls or storiform patterns, features typical of benign perineurioma, were selected. On the basis of immunohistochemistry (EMA + / S-100 -), 5 perineurial MPNST were found in 23 tumors selected. Therefore, 4% of MPNST (5 of 121) show perineurial cell differentiation. An NE-1 association has yet to be described. Nerve involvement is infrequent. Their immunophenotype (EMA + / S-100 -) frequently indic … More ates ultrastructural perineurial differentiation. The prognosis of perineurial MPNST appears to be more favorable than that of conventional MPNST.FISH analyses using paraffin embedded materials failed to show centromere signals.2.Sclerosing perineuriomaScierosirig perineurioma, a new subtype of soft part perineurioma, frequently arises in the dermis and subcutis of the hands. Microscopically, tumors consisted of spindle-shaped or epithelioid cells in a dense stroma, often arranged in cords or clusters. Most tumor cells were positive for EMA, whereas they lacked immunoreactivity for S-100 protein. Ultrastructural studies clearly showed perineunal cell characteristics.3.Perineurial cells in varied peripheral nerve sheath tumorsTo demonstrate the participation of perineurial cells in PNST, the catalyzed signal amplification (CSA) method, a highly sensitive immunohistochemical method, was applied to varied tumors. In result, many EMA-positive spindle-shaped cells were identified in neurofibromas, indicating that the perineurial cells are one of principal constituents of this type of tumor. Schwannomas were surrounded by EMA-positive perineurium. Less