Olfactory neuroblastoma A Review

Introduction:

Olfactory neuroblastoma is a very rare malignant tumor seen involving the nasalcacity. This tumor is of neuroectodermal origin. It arises from theolfactory epithelium that lines the upper 1/3 of nasal septum,cribriform plate and corresponding medial portion of superiorturbinate. This tumor presents in the upper part of the nasal cavity commonly as a hemorrhagic mass with evidence of bone destruction.

Age incidence:

Well differentiated olfactory neuroblastomas commonly occur in patientsduring 5th decade of life. Less differentiated olfactory neuroblastomasoccur in patients during their 2nd decade of life. This tumorconstitutes 2% of all malignant tumors of nose and paranasal sinuses.

Signs & Symptoms:

1. Most common symptom is unilateral nasal obstruction and congestion

2. Pain and proptosis of eye if orbit is involved

3. Excessive lacrimation

4. Ear pain and otitis media due to eustachean tube obstruction

5. Presence of frontal headache suggests involvement of frontal sinus

6.Neurological manifestations due to intracranial extension is prettylate in the course of the disease because frontal lobe of brain is asilent area.

Anterior rhinoscopy reveals a reddish brown polypoidal mass in the roof of the nasal cavity.

Radiographic features:

Varies depending on the extent of involvement. In early stages the tumor maybe seen in the superior portion of nasal cavity. There is associatedopacification of ethmoid sinus. In advanced lesions there may bedestruction of ethmoidal sinuses, maxillary sinuses with completeopacification of the whole of nasal cavity. There may also beassociated destruction of middle and inferior turbinates. CT scanimaging of nose and paranasal sinuses helps in delineating the bonylandmarks inside the nasal cavity.

Staging:

Plays a vital role in determining the prognosis of the disorder and also todetermine the treatment modality. Since this is a very rare malignanttumor there is no universally acceptable staging protocol. Mostacceptable of all the staging protocols is based on Kadishclassification system.

Stage A tumors: Tumors of this stage are confined to the nasal cavity

Stage B tumors: Involves the paranasal sinuses

Stage C tumors: Involves middle cranial fossa and retrobulbar orbit

Hyam's classification is based on histological differentiation of the tumor.It grades the tumor from I - IV. Stage IV is undifferentiated tumorwhile the other stages indicated varying stages of differentiation.

Histopathology:

Microscopically, the tumor is characterized by rounded compact cellular foci. Thesecells are discrete and are separated by a very vascular stroma. Thenucleus of the tumor cells may be oval / round and stains deeply. Thesecells have more cytoplasm. Presence of rosette may be seen. Therosette if present belong to the true rosette category consisting ofcuboidal / columnar cells about a central space resembling a glandularstructure (Flexner rosette). Sometimes these cells may enclosefibrillary / granular material (Holmer wright rosette). These rosettesshould not be confused with pseudorosettes where in the cells arearranged around blood vessels.

Electron microscopy:

The tumor cells are polygonal / spherical in shape. They contain largerounded nucles. Nucleoli may be present. There is a profuse network ofneurites attached to the cells forming synaptic connections. Many ofthese cells contain neurosecretary granules. Catecholamines have beenfound to be present in abundance inside these cells.

Increased urinary excretion of catecholamines have been demonstrated in some of these patients.

Metastasis:

Tumor metastasis occur in 20% of these cases. Metastasis to lymph nodes, lungs and bones are common.

Management:

This tumor can be managed by surgical resection followed by full course irradiation.