Hyam’s Grading System

• The Hyam’s Grading System is a pathologic grading system for esthesioneuroblastoma, also known as olfactory neuroblastoma (ONB).¹²
  • In combination with the Kadish Staging System, this is used to prognosticate and guide treatment decisions in patients with olfactory neuroblastomas.
• The low grade pattern encompasses Hyams Grade I and II.
• The high grade pattern encompasses Hyams Grade III and IV.
• Low grade olfactory neuroblastomas have a lobular architecture with well defined groups of tumor cells with a surrounding fibrillary matrix.
  • Homer Wright Rosettes are a characteristic feature of Grade I/II ONBs, but are not always present.
• High grade olfactory neuroblastomas grow as diffuse sheets of cells with the presence of foci of necrosis and scarce but highly vascularized stroma.
  • Flexner-Wintersteiner Rosettes are only seen in Grade III ONBs.

Hyam’s Grading System for Olfactory Neuroblastoma