Ependymal rosettes (ependymoma)

Ependymal rosettes correspond to a histologic architectural pattern that very characteristic of ependymomas, as tumor cells form structures similar to the lining of normal ventricles. They are characterized by a halo or spoke-wheel arrangement of tumor cells surrounding an empty central tubule lumen.

They should not be confused with the far more common perivascular pseudorosettes.

Differential diagnosis

In addition to perivascular pseudorosettes, an ependymal rosette should be differentiated from:

• Homer Wright rosette: central lumen filled with fiber-like processes
• Flexner-Wintersteiner rosette: central lumen contains small cytoplasmic extensions of the encircling cells
• pineocytomatous and neurocytic rosettes:  generally larger and more irregular in contour