Olfactory neuroblastoma

Olfactory neuroblastoma
Diagnosis in short
Olfactory neuroblastoma
LM	small round (blue) cell tumour (stippled chromatin, high NC ratio), +/-Flexner-Wintersteiner rosette (rosette with empty centre), +/-Fibrillary, eosinophilic material (neuropil-like)
LM DDx	other small round blue cell tumours (e.g. small cell carcinoma of the lung), large cell lymphoma (e.g. DLBCL), basaloid squamous cell carcinoma
Prevalence	rare
Prognosis	poor

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

• Neuroendocrine markers:
  • CD56 +ve.
  • Synaptophysin +ve.
  • Chromogranin A +ve.
  • NSE +ve.
    • Lower expression of neuroendocrine markers in IDH2 mutant tumors.^{[citation needed]}
• S-100:
  • Small round cells -ve.
  • Sustentacular cells +ve.
    • Neuronal ONB subtype is enriched for the presence of S100 sustentacular cells.

Others:

• CD45 -ve (r/o lymphoma).
• AE1/AE3 usually -ve (~1/3 are +ve).
• 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.