 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.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.