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Olfactory neuroblastoma

Introduction:

Olfactory neuroblastoma is a very rare malignant tumor seen involving the nasal cacity. This tumor is of neuroectodermal origin. It arises from the olfactory epithelium that lines the upper 1/3 of nasal septum, cribriform plate and corresponding medial portion of superior turbinate.
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 patients during 5th decade of life. Less differentiated olfactory neuroblastomas occur in patients during their 2nd decade of life. This tumor constitutes 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 pretty late in the course of the disease because frontal lobe of brain is a silent 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 may be seen in the superior portion of nasal cavity. There is associated opacification of ethmoid sinus. In advanced lesions there may be destruction of ethmoidal sinuses, maxillary sinuses with complete opacification of the whole of nasal cavity. There may also be associated destruction of middle and inferior turbinates. CT scan imaging of nose and paranasal sinuses helps in delineating the bony landmarks inside the nasal cavity.

Staging:

Plays a vital role in determining the prognosis of the disorder and also to determine the treatment modality. Since this is a very rare malignant tumor there is no universally acceptable staging protocol. Most acceptable of all the staging protocols is based on Kadish classification 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 tumor while the other stages indicated varying stages of differentiation.

Histopathology:

Microscopically, the tumor is characterized by rounded compact cellular foci. These cells are discrete and are separated by a very vascular stroma. The nucleus of the tumor cells may be oval / round and stains deeply. These cells have more cytoplasm.
Presence of rosette may be seen. The rosette if present belong to the true rosette category consisting of cuboidal / columnar cells about a central space resembling a glandular structure (Flexner rosette). Sometimes these cells may enclose fibrillary / granular material (Holmer wright rosette). These rosettes should not be confused with pseudorosettes where in the cells are arranged around blood vessels.

Electron microscopy: The tumor cells are polygonal / spherical in shape. They contain large rounded nucles. Nucleoli may be present. There is a profuse network of neurites attached to the cells forming synaptic connections. Many of these cells contain neurosecretary granules. Catecholamines have been found 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.
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