Flexner-Wintersteiner rosette

Flexner–Wintersteiner rosette is a spoke and wheel shaped cell formation seen in retinoblastoma and certain other ophthalmic tumors. A rosette is a structure or formation resembling a rose, such as the clusters of polymorphonuclear leukocytes around a globule of lipid nuclear material, as observed in the test for disseminated lupus erythematosus.

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). Flexner noted characteristic clusters of cells in an infantile eye tumor which he called retinoepithelioma. A few years later, in 1897, Austrian ophthalmologist Hugo Wintersteiner (1865–1946) confirmed Flexner’s observations and noted that the cell clusters resembled rods and cones. These characteristic rosette formations were subsequently recognized as important features of retinoblastomas.

The tumor cells that form the Flexner–Wintersteiner rosette surround a central lumen containing small cytoplasmic extensions of the encircling cells. Unlike the center of the Homer Wright rosette, the central lumen is devoid of fiber-rich neuropil. Like the Homer Wright rosette, the Flexner–Wintersteiner rosette represents a specific form of tumor differentiation.Electron microscopy reveals that the tumor cells forming the Flexner–Wintersteiner rosette have ultrastructural features of primitive photoreceptor cells. 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. In addition to being a characteristic finding in retinoblastomas, Flexner–Wintersteiner rosettes may also be found in pinealoblastomas and medulloepitheliomas.

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