rosette

1. The quartan malarial parasite Plasmodium malariae in its segmented or mature phase. 2. A grouping of cells characteristic of neoplasms of neuroblastic, neuroectodermal, or ependymal origin; a number of nuclei form a ring from which neurofibrils, which can be demonstrated by silver impregnation, extend to interlace in the center (Homer-Wright r.). 3. Roselike coiling of the uterus among certain pseudophyllidean tapeworms, such as Diphyllobothrium latum. 4. Cells of one type surrounding a cell of another type. [Fr. a little rose]

- E r. (ro-zet′) the adherence of erythrocytes to cells. Sheep erythrocytes will adhere spontaneously to human T cells, forming rosettes.

- EAC r. indicates the presence of complement receptors. Erythrocytes (E) coated with antibody (A) and complement (C) are incubated with test cells; if the test cells have complement receptors, the EAC will adhere to these cells, forming rosettes.

- Homer-Wright rosettes pseudorosettes formed by the arrangement of tumor cells around an area of fibrillarity, evidence of neuroblastic differentiation in a medulloblastoma or primitive neuroectodermal tumor.

- Wintersteiner rosettes rosettes found only in retinal embryonic tumors, formed by a group of columnar cells with a peripheral basement membrane arranged in a radial manner around a central cavity, the spokes corresponding to the photoreceptors.

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ro·sette rō-'zet n a rose-shaped cluster of cells

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ro·sette (ro-zetґ) [Fr. “little rose”] a structure, formation, or part occurring in a loosely attached cluster resembling a rose, such as (a) the clusters of polymorphonuclear leukocytes around a globule of lysed nuclear material, observed in a test for systemic lupus erythematosus; (b) a unique glandular complex near the oral area of certain ciliate protozoa, of unknown function; or (c) the symmetrical segmenter stage of certain malarial parasites, especially Plasmodium malariae.