Embryonal Tumor with Abundant Neuropil and Ependymoblastic Rosettes David W. Ellison St. Jude Children’s Research Hospital Memphis, TN

Clinical History The patient is a male infant presenting at the age of 18 months with symptoms and signs of raised intracranial pressure. MRI revealed a mass in the right frontal lobe, which was removed without apparent residual. Adjuvant chemotherapy failed to prevent relapse at 9 months, and overall survival was 12 months. Slide 1 Click to view with ImageScope Click to view with a Web-Based Viewer Figure 1 A neuroepithelial tumor with contrasting regions of high / low cell density and rosette formation is evident. Figure 2 Extensive low cell density regions contain a neuropil-like matrix, in which oval and round nuclei occasionally with a single nucleolus are embedded. Figure 3 High cell density regions contain undifferentiated embryonal cells, some of which form ependymoblastic rosettes. Figure 4 Widespread neuropil-like regions are synaptophysin-immunopositive. Figure 5 Clusters and rosettes of embryonal cells are synaptophysin-negative. Figure 6 Scattered embryonal cells are immunoreactive for neurofilament proteins. Figure 7 Scattered large differentiated cells are immunoreactive for neuronal nuclear antigen (NEU-N). Figure 8 The luminal surface of rosette-forming cells shows immunoreactivity for epithelial membrane antigen (EMA). Figure 9 Cell proliferation, as assessed by Ki-67 immunolabeling, is high in regions of embryonal cells and in rosettes, but low or absent in neuropil-like regions. Figure 10 Cell proliferation, as assessed by Ki-67 immunolabeling, is high in regions of embryonal cells and in rosettes, but low or absent in neuropil-like regions. Differential Diagnosis Embryonal tumor with abundant neuropil and ependymoblastic rosettes Ependymoblastoma CNS primitive neuroectodermal tumor (PNET), WHO grade IV Final Diagnosis Embryonal tumor with abundant neuropil and ependymoblastic rosettes Key words: brain tumor, ependymoblastoma, embryonal tumor, WHO classification References McLendon RE, Judkins AR, Eberhart CG et al. Central nervous system primitive neuroectodermal tumours. In: Louis DN, Ohgaki H, Wiestler OD and Cavenee WK eds. WHO classification of tumours of the central nervous system. Lyon: IARC, 2007: 141-146. Eberhart CG , Brat DJ , Cohen KJ et al. Pediatric neuroblastic brain tumors containing abundant neuropil and true rosettes. Pediatr Dev Pathol. 2000; 3(4): 346-52. Dunham C , Sugo E , Tobias V et al. Embryonal tumor with abundant neuropil and true rosettes (ETANTR): report of a case with prominent neurocytic differentiation. J Neurooncol. 2007; 84(1): 91-8.