 The cells of the pineocytomatous/neurocytic rosettes are also considered to be much more differentiated than the cells forming Homer Wright rosettes in that the nuclei are slightly larger, more rounded, much less mitotically active, and paler or less hyperchromatic.In rare cases, these rosettes may aggregate in a sheet of back-to-back clusters resembling field stone pavement.The neuropathologic diagnosis of brain tumors entails the microscopic examination of conventional formalin-fixed paraffin-embedded tissue samples surgically removed from a radiographically defined lesion.