Flexner-Wintersteiner rosettes

Flexner-Wintersteiner rosettes may also be observed.

In addition, Flexner was the first to describe Flexner-Wintersteiner rosettes, a characteristic finding in retinoblastoma.

In addition to being a characteristic finding in retinoblastomas, Flexner-Wintersteiner rosettes may also be found in pinealoblastomas and medulloepitheliomas.

Histology shows similarity to neuroblastoma and medulloblastoma, including aggregation around blood vessels, necrosis, calcification, and Flexner-Wintersteiner rosettes.

Furthermore, the rosette lumen shows similar staining patterns as in rods and cones, suggesting that Flexner-Wintersteiner rosettes represent a specific form of retinal differentiation.

Flexner-Wintersteiner rosettes were first described by Simon Flexner (1863-1946), a physician, scientist, administrator, and professor of experimental pathology at the University of Pennsylvania (1899-1903).

Undifferentiated elements appear as collections of small, round cells with hyperchromatic nuclei; differentiated elements include Flexner-Wintersteiner rosettes, Homer-Wright rosettes, and fluerettes from photoreceptor differentiation.