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Olfactory neuroblastomas (Esthesioneuroblastomas)

Olfactory neuroblastomas present with nasal obstruction, rhinorrhea, or epistaxis, often with delayed presentation. They are sinonasal tumors arising from the basal layer of olfactory epithelium in the superior recess of the nasal cavity, with 25-30% extending intracranially at diagnosis.

Key Images

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Look For First
  • Soft tissue mass in the superior olfactory recess of the nasal cavity with involvement of anterior and middle ethmoid air cells
  • Dumbbell-shaped configuration with a waist as the mass passes through the cribriform plate
  • Heterogeneous enhancement on CT and MRI with variable but usually moderate to intense gadolinium enhancement
  • Peritumoural cysts along the intracranial margin when there is anterior cranial fossa extension
Key Image Findings
  • CT demonstrates soft tissue attenuation mass with relatively homogeneous enhancement and occasional focal calcifications; bony margins show remodeling and resorption rather than aggressive destruction due to slow growth pattern
  • MRI shows heterogeneous intermediate signal on both T1 and T2 sequences with variable to intense gadolinium enhancement that may be less homogeneous than on CT
  • The mass characteristically originates in the superior olfactory recess and initially involves anterior and middle ethmoid air cells unilaterally, expanding from this origin point
  • Classic dumbbell-shaped morphology results from the tumor's expansion superiorly through the cribriform plate into the anterior cranial fossa and laterally into the orbits and across midline
  • Peritumoural cysts are often present along the intracranial margin when cranial fossa extension occurs, with enhancement at the cyst margins that can help distinguish from other entities
  • The tumor may obstruct paranasal sinus ostia, resulting in secondary opacification of sinuses with secretions
  • Cervical and retropharyngeal nodal metastases are present in 10-44% of cases at diagnosis and should be specifically evaluated
  • DSA demonstrates prominent tumor blush with arteriovenous shunting and persistent opacification, and MIBG nuclear medicine imaging shows avidity helping differentiate from other sinonasal tumors
Differential Diagnosis
  • Olfactory groove meningioma or solitary fibrous tumor of the dura: superior extension pattern can mimic; distinguished by location more anterior on meningioma and different imaging characteristics
  • Sinonasal carcinoma (squamous cell, minor salivary gland adenocarcinoma): may appear identical radiographically; typically older patients, lack peritumoural cysts, epicenter more variable
  • Lymphoma: may appear identical on imaging; distinguished by lack of peritumoural cysts and different clinical presentation
  • Nasopharyngeal carcinoma: epicenter more posteriorly located and typically in older patients, distinguishing from superior olfactory recess origin
  • Juvenile nasopharyngeal angiofibroma: epicenter more posteroinferiorly located, almost exclusively males, younger age group
  • Chordoma: epicenter more posteriorly located with characteristically high T2 signal intensity
Discussion

Olfactory neuroblastomas arise from neural crest cell-derived olfactory epithelium and demonstrate bimodal age distribution with peaks in the 2nd decade and 5th-6th decades

Presentation is often delayed with patients presenting late as the tumor can grow silently for months before causing nasal symptoms like obstruction, rhinorrhea, or epistasis

The slow-growing nature of these tumors results in bone remodeling rather than aggressive destruction, visible as gradual resorption of bony margins on imaging

Approximately 25-30% of patients present with intracranial extension into the anterior cranial fossa at the time of diagnosis

Prognosis is significantly affected by presence of distant metastases, with 60% five-year survival without distant metastases versus 0% survival with distant metastases

Small localized tumors have favorable prognosis with 85-90% cure rates when treated with combined chemotherapy, radiotherapy, and surgical excision

Reporting Pearls

Describe the mass as originating in the superior olfactory recess with unilateral ethmoid involvement, specify the direction of extension (intracranial, orbital, contralateral), characterize the enhancement pattern, note the presence or absence of peritumoural cysts if intracranial extension is present, and explicitly evaluate for cervical and retropharyngeal adenopathy given the 10-44% prevalence at diagnosis.

Pitfalls
  • Imaging alone cannot reliably distinguish olfactory neuroblastomas from other aggressive malignancies in the region, requiring clinical correlation and often histopathology for definitive diagnosis
  • Failure to specifically evaluate cervical and retropharyngeal lymph nodes for metastases, which are present in 10-44% of cases and affect staging and prognosis
  • Mistaking the presence of peritumoural cysts as a distinguishing feature that is present in olfactory neuroblastoma but absent in carcinomas and lymphomas, requiring knowledge of this imaging characteristic
  • Underestimating intracranial extension by focusing only on the sinonasal component; approximately 25-30% of patients present with anterior cranial fossa involvement that must be carefully assessed
Source: Reference source

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