Rosette Perivascular pseudorosette 2018-07-04T13:30:24Z A type of rosette in which a spoke-wheel arrangement of cells with tapered cellular processes radiates around a wall of a centrally placed vessel. The modifier pseudo differentiates this pattern from the Homer Wright and Flexner-Wintersteiner rosettes, perhaps because the central structure is not actually formed by the tumor itself, but instead represents a native, non-neoplastic element. Also, some early investigators argued about the definition of a central lumen, choosing pseudo to indicate that the hub was not a true lumen but contained structures. Nevertheless, this pattern remains extremely diagnostically useful and the modifier unnecessarily leads to confusion. Perivascular pseudorosettes are encountered in most ependymomas regardless of grade or variant.