Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. 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).