Olfactory neuroblastoma

Olfactory neuroblastoma, also known as esthesioneuroblastoma, is a rare aggressive tumour of the head and neck.

Neuroblastoma is dealt with in the neuroblastoma article.

General

Epidemiology:

• Prognosis: poor.
• Wide age range with bimodal distribution - teens and 60s.
• No sex predilection.

Clinical presentation:

• Nasal obstruction ~ 70%.
• Epistaxis ~ 50%.
• Anosmia.
• Headache.

Gross

• Arises from olfactory mucosa - upper nasal cavity.

Microscopic

Features:

• Small round (blue) cell tumour with:
  • Stippled chromatin.
  • High NC ratio.
• +/-Flexner-Wintersteiner rosette - rosette with empty centre (donut hole).
• +/-Fibrillary, eosinophilic material (neuropil-like).

DDx:

• Lymphoma.
• Small cell carcinoma.
• Other small round cell tumours.
• Basaloid squamous carcinoma.^{[citation needed]}

Images:

• Olfactory neuroblastoma - crappy image (upmc.edu).
• Olfactory neuroblastoma (nih.gov).

• 

  Olfactory neuroblastoma (H&E).

• 

  Olfactory neuroblastoma (AFIP).

• 

  Sustenticular cells in ONB (AFIP).

IHC

• S-100:
  • Small round cells -ve.
  • Sustentacular cells +ve.
    • Neuronal ONB subtype is enriched for the presence of S100 sustentacular cells.
• Neuroendocrine markers +ve (CD56, synaptophysin).
  • lower expression of neuroendocrine markers in IDH2 mutant tumors.

Others:

• CD45 -ve (r/o lymphoma).
• AE1/AE3 usu. -ve (r/o carcinoma).
• CAM5.2 usu. -ve -- up to 35% +ve.
  • Higher expression of cytokeratins in IDH2 mutant tumors.

Molecular

• Two major subgroups.
  • Classical ("neural").
  • Basal: G-CIMP+ve with frequent IDH2 R172 mutations.

See also

• Small round cell tumours.
• Head and neck pathology.