Homer Wright rosettes

The cytoplasm is scanty, poorly defined, and frequently pale owing to an abundance of glycogen. Homer Wright rosettes may be seen, as well as rare Elexner-Wintersteiner rosettes. Mitoses are highly variable. 

Medulloblastoma/ pineoblastoma/ neuroblastoma/PNET Slight fibrillarity (Homer-Wright rosettes) (palisades) "carrot" nuclei (neural or glial foci) Synaptophysin (-r) PCP9.5 S-100 neurofilament (R) GFAP (R) Cerebellum brainstem pineal CNS (extra-axial) ... 

ONE is composed of cells with poorly defined cytoplasm and prominent, uniformly round nuclei with barely discernible nucleoli. The tumor cells are usually quite bland, with minimal pleomorphism. ONE tumor cells have neuroendocrine-type chromatin with minimal hyper-chromasia. The cells grow in a lobular, diffuse, or mixed lobular-diffuse pattern (Fig. 9.4). Rosettes, especially Homer Wright and exceptionally Flexner-Wintersteiner, may be seen. Necrosis and mitoses are uncommon. The stroma is highly vascular and, at times, neurofibrillary. 

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