ABSTRACT
Objective To investigate the imaging findings and pathological characterislics of primitive neuroectodennal tumor (PNET). Meth-ods Imaging data of 22 cases of PN ET confirmed by pathology were retrospectively analyzed. Results There were 5 cases of central PNET, which were round or lobulated masses, 4 cases with cystic degeneration, 1 case with necrosis, and 4 cases with mild peritu moraledema. Magnetic resonance imaging (MRI) revealed isointensity or slightlyhy pointensity on Tl-and hyperin tensity on T2-weighted imag-es, and marked heterogeneous enhancement. There were 17 cases of peripheral PNET, which were mostly large lobulated soft tissue mass-es, 7cases with cystic degeneration, 3 cases with necrosis, and 8 cases with boned estructio n. Computed tomography (CT) scan showed iso-lowd ensity. MRI revealed isointensity or slightly hypointensity on Tl-and heterogeneous hypeiintensityon T2-weighted images, and marked heterogeneous enhancement. Hematoxylin-eosin staining showed Homer-Wright rosette arrangement of the tumor cells in 13 cases. Immunohistochemical staining revealed expression of CD99 (17/22), CD56 (16/18), Ki-67 (22/22), and vimentin (22/22) by the tumorcells. Conclusion MRI and CT findings of PNET are characteristic and helpful in differential diagnosis of the disease. CD99 is of signif-icant value as a diagnostic biomarker and in the classification of PNET.