Search

A 22-year-old man presented with tenderness and swelling of the left lateral part of the orbit. Computed tomography revealed a left intraorbital mass measuring 3 cm × 3 cm involving the left lateral wall of the orbit and the greater wing of the left sphenoid bone. Magnetic resonance imaging revealed that the intraorbital mass was extraneuroaxial. During surgery, the tumor was seen to arise from the lateral wall of the orbit and infiltrate into the left temporal muscle. Following the surgery, the patient was administered radiation therapy for the whole cranium and chemotherapy for the residual tumors. However, the tumor recurred, and the patient died about 2 years following the first surgery because the tumor had metastasized to the lung. On light microscopy, the tumor cells were closely packed with uniform, small, and round cells. Immunohistochemical studies showed that the tumor cell membrane stained positive for MIC2. Furthermore, the MIB-1 labeling index was 36.2%. On electron microscopy, small quantities of cytoplasm containing glycogen accumulations without neurosecretory granules and neurofilaments were observed. Based on these results, the tumor was diagnosed to be primary Ewing’s sarcoma. Primary orbital Ewing’s sarcoma of the skull has been considered to be extremely rare, and a review of the literature was performed. [ABSTRACT FROM AUTHOR]

Background. Recent immunocytochemical and cytogenic studies have shown that Ewing's sarcoma and peripheral primitive neuroectodermal tumor (PNET) are probably related neoplasms of common neuroectodermal origin. The purpose of this study was to investigate the morphological characteristics of neural differentiation in these tumors. Methods. We investigated the ultrastructure of 17 cases of Ewing's sarcoma and related tumors in the specimens of 17 patients, and carried out immunohistochemical analysis. Results. Ultrastructurally, the cell process and basal laminae were frequently observed in all cases of an unclassified small round-cell type of malignant peripheral nerve sheath tumor (MPNST-related tumor). In contrast, a poorly developed cell process and fragmented basal lamina were rarely observed in Ewing's sarcoma or in PNET. Cytoplasmic neurosecretory granule-like particles were found in two specimens of Ewing's sarcoma and two of PNET, and were abundant in one MPNST-related tumor specimen. These ultrastructural neural features were not common in Ewing's sarcoma, and were occasionally present in PNET. There was a discrepancy between positivity for immuno-neural markers and ultrastructural neural features. Conclusion. The differential diagnosis between Ewing's sarcoma and PNET was based on the degree of their morphological neural differentiation. Thus, we consider that the diagnosis of PNET should be made on the basis of ultrastructural neural features, taking into account immunohistochemical and histological considerations. [ABSTRACT FROM AUTHOR]