NEURORADIOLOGY

Imaging Findings:

Study shows a hyperdense, minimally enhancing mass lesion in the left superior nasal cavity, with bony erosion of the adjoining medial orbital wall, and sphenoid wall involvement. No calcification is noted.

Diagnosis:

Esthesioneuroblastoma

Discussion

Introduction

Esthesioneuroblastoma (ENB) is an uncommon malignant neoplasm of neural crest origin arising from the olfactory sensory epithelium in the roof of the nasal fossa. The tumor was first described in 1924 by Berger et al, who reported in the French literature about "l'esthesioneuroepitheliome olfactif."

Spread

ENB tends to spread submucosally in all directions to involve the paranasal sinuses, nasal cavity, and surrounding structures. The tumor is locally aggressive, and local recurrence strikes in up to 68% of cases regardless of initial treatment protocol. ENB also metastasizes widely by both hematogenous and lymphatic routes, with the neck being the most common site.

Histology

Common features on histology which aid in identification include small, round or oval blue neuroepithelial cells arranged in true rosette of pseudorosette patterns, separated by fibrous septa, surrounding stroma composed of undifferentiated nuclei and neurofibrillary cords; marked microvascularity; palisading of neuroepithelial cells around vessels. Mitotic figures are rare, and calcification and necrosis are sometimes seen. Occasionally, electron microscopy is used to confirm the presence of neuroblastoma.

Imaging

The advent of CT scanning has greatly enhanced the staging accuracy and therapeutic planning capability with regard to ENB. ENB has no classic radiologic features, but the tumor is typically a homogenous soft tissue mass with relatively uniform, moderately intense contrast enhancement, located in the superior nasal cavity. Bony erosion is frequently seen and usually accompanied by remodeling. Calcification may be seen.

Staging

Kadish et al in 1976 devised the currently popular staging system for ENB. 

Group A: tumor confined to the nasal cavity;

Group B: tumor involving the nasal cavity and paranasal sinuses;

Group C: tumor extension beyond the nasal cavity and sinuses.

Biller et al proposed a staging system based on the TNM classification:

T1: tumor in the nasal cavity and sinuses (except sphenoid) with or without erosion of anterior cranial fossa bone

T2: periorbital or anterior cranial fossa extension

T3 brain involvement with resectable margins

T4 unresectable tumor.

Treatment

Primary surgery, primary radiotherapy, and combined surgery and radiotherapy have been employed against ENB. Chemotherapy has generally not been the first choice for resectable ENB, but a multitude of drugs have achieved cytoreduction in advanced cases in some studies.

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