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Rare Schwannoma in Lateral Nasal Wall

Rare Schwannoma in Lateral Nasal Wall

Overview 

Schwannomas are a mass of tumors in the peripheral nervous system (PNS). They are abnormal and usually have a benign proliferation of Schwann cells. Because of this, any type of neoplasms can usually occur anywhere in the body. However, reports have shown that the most common site of schwannoma found in the head and neck region is the cerebellopontine angle. There are also many articles that have found schwannoma in areas such as the pharynx, larynx, scalp, parotid, and even oral cavities. Only 4% of head and neck schwannomas are found in the sinonasal region. 

Case Report 

This case is a rare type of schwannoma originating from the lateral nasal wall. It follows a 70 year old male with the unilateral progressive nasal obstruction which started two years ago according to the otolaryngology department of Taleghani Hospital in Tehran, Iran. 

Based on the reports, the patient was working in the textile industry. He had no history of nasal trauma, disorder, cough, sneezing, headache, or any form of facial pain. His only medical history was type 2 diabetes mellitus. 

His nasal endoscopy showed that there was a space-occupying mass in his right nasal vestibule. It was big enough to prevent further observation in the area. Although his larynx, pharynx, head, and neck were normal. Scans showed that the mass with mild heterogenous enhancement had no destructive effect on adjacent structures. 

What are Schwannomas? 

Schwannomas are benign slow-growing masses that are often less destructive in nature. Obstruction in the nasal cavity is the most common clinical presentation in nasal cavity schwannoma. There are also reported symptoms which include visual defects, facial nerve palsy, facial pain, and exophthalmos. 

For the head and neck region, neck soft tissue, parapharyngeal space, and oropharynx are the most commonly diagnosed locations. Schwannomas in the nasal cavity are extremely rare accounting for only around 20 reported cases in literature. 

Based on studies of this phenomenon, the nasal cavity schwannoma originates from the nasal septum, and only in one case, it was found to be from the nasal sidewall. The disease also usually occurs in people around 50-60 years of age. There are also no gender or race factors that affect its occurrence. 

It has been reported that nasal cavity schwannomas originate from the maxillary and ophthalmic nerves, sphenopalatine ganglion, and other nerves that innervated the nasal mucosa. In the subject of the study, the nasal cavity schwannoma originated from the lateral nasal wall, and given that the lateral wall is innervated by the anterior ethmoidal nerve, lateral posterior inferior nasal, and lateral posterior superior nasal. 

It shows that the aforementioned schwannoma is associated with the above nerve. Also, due to the complex pathomechanism of schwannoma, it is not possible to make a definite statement about the origin of this type of schwannoma and the issue is open to as previously mentioned, the pathomechanism of schwannoma is very complex and several factors are involved in its development. It has been suggested that oxidative stress plays a crucial role in the pathogenesis of schwannoma.

In the nasal vestibule, nasal schwannomas are usually present with unilateral nasal obstruction, pain, and sometimes facial numbness. The tumor is often slow-growing and grows in medium size only. However, nasal vestibular schwannomas develop symptomatic earlier and are smaller at presentation. As a result, they are usually excised without the need for radiologic imaging.

Macroscopically, schwannomas appear as gelatinous. They are often well-encapsulated masses. They are classified into two types: Antoni A which are areas of high cellularity with spindle-shaped cells, and Antoni B characterized by loose myxoid stroma with spindle cells running in a haphazard manner. 

The diagnosis of a nasal tumor includes a wide variety of pathology including inflammatory polyps, meningioma, neurofibroma, and olfactory neuroblastoma. Treatment is often surgical excision. The surgical approach is determined according to the location and extent of the lesion. Recurrences of nasal schwannomas are rare. 

Discussion 

From data gathered from previous literature, there are some cases of nasal schwannoma where the patient also had diabetes mellitus. In this case, the patient had diabetes for 4 years already.  Although diabetes mellitus increases free radicals through lipotoxicity and glucotoxicity, the researchers cannot say certainly that diabetes has been one of the risk factors for schwannoma for the patients, and this requires precise cellular and molecular studies. Differential diagnosis between different tumors of the nasal cavity such as squamous cell carcinoma, schwannoma, lymphoma, fibrous dysplasia, chondrosarcoma, and extension of the angiofibroma of the nasopharynx is very difficult based on clinical findings. 

Furthermore, medical imaging such as CT scans may not provide valuable findings for differential diagnosis, but they are useful in evaluating the size, diameter, and extent of the mass. The most accurate method for the definitive diagnosis of schwannoma is histopathological assays. Schwannomas generally have a smooth appearance and are covered by a capsule derived from the perineurium of the nerve. 

These tumors also grow eccentrically to the nerve from which they arise. Another diagnostic criterion is the presence of spindle cells with a basophilic histological pattern. In the present study, the pathology report described a benign spindle cell neoplasm that was compatible with schwannoma.

In the macroscopic view, schwannoma is lonely, well-demarcated with a round or oval shape, yellowish to grayish in color, and shiny on cutsurface.6In our study, the macroscopic appearance of the mass was in accordance with schwannoma criteria, but as mentioned, it has no high diagnostic value.

According to the nature of schwannoma, excision by external approach or endonasal surgery is the treatment of choice based on tumor size and extension. With this in mind, in our case due to the tumor size and its limited extension, the endonasal approach was selected.

Conclusion

Nasal cavity schwannoma is extremely rare. An accurate diagnosis is made only with histopathological reports. It seems that nasal cavity schwannomas originate from trigeminal nerve branches, but the issue is open to discussion. Furthermore, endoscopic surgery is an efficient method to remove most of the benign mass of the nasal cavity such as schwannoma.

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