Rosettes in Pathology

Rosette refers to a decoration or pattern resembling a rose.

rosette types

In pathology, rosette refers to aa halo or “spoke-wheel” arrangement of cells around a central structure especially in neoplasms of neuroblastic or neuroectoderma origin. The central structure can be:

a. Empty lumen: True ependymal rosette

  1. Well differentiated ependymomas (minority of cases)
  2. Ependymoblastoma (rare form of PNET)

b. Meshwork of fibers (Neuropil): Homer-Wright rosette

Remember: It is Neuropil and not neutrophil. Neuropil refers to primitive neuronal processes or neurites.

  1. Medulloblastoma
  2. Supratentorial PNETs
  3. Pineoblastoma
  4. Retinoblastoma

c. Cytoplasmic extensions of encircling tumor cells: Flexner-Wintersteiner rosette

  1. Retinoblastoma
  2. Pineoblastoma
  3. Medulloepithelioma

Fleurettes: This refers to tumor cell’s attempt for photoreceptor differentiation.

d. Blood vessel: Perivascular pseudorosette

This is pseudorosette because the central structure is not actually formed by the tumor itself, but instead represents an arrangement of cells around native, non-neoplastic element.

  1. Medulloblastoma
  2. PNETs
  3. Central neurocytoma
  4. Pilomyxoid astrocytoma

Glomeruloid bodies are like pseudovascular rosette. They are seen in:

  1. Glioblastoma multiforme
  2. Schiller-Duval bodies of Endodermal sinus – Yolk sac tumor.

e. Irregular large lumen with neuropil (similar to Homer-Wright rosette): Neurocytic rosette

  1. Central neurocytoma

Also, rosetting of erythrocytes in peripheral blood smear (PBS) is seen in Malaria (Plasmodium infection).

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