Why are olfactory ensheathing cell tumors so rare?

The glial cells of the primary olfactory nervous system, olfactory ensheathing cells (OECs), are unusual in that they rarely form tumors. Only 11 cases, all of which were benign, have been reported to date. In fact, the existence of OEC tumors has been debated as the tumors closely resemble schwannomas (Schwann cell tumors), and there is no definite method for distinguishing the two tumor types. OEC transplantation is a promising therapeutic approach for nervous system injuries, and the fact that OECs are not prone to tumorigenesis is therefore vital. However, why OECs are so resistant to neoplastic transformation remains unknown. The primary olfactory nervous system is a highly dynamic region which continuously undergoes regeneration and neurogenesis throughout life. OECs have key roles in this process, providing structural and neurotrophic support as well as phagocytosing the axonal debris resulting from turnover of neurons. The olfactory mucosa and underlying tissue is also frequently exposed to infectious agents, and OECs have key innate immune roles preventing microbes from invading the central nervous system. It is possible that the unique biological functions of OECs, as well as the dynamic nature of the primary olfactory nervous system, relate to the low incidence of OEC tumors. Here, we summarize the known case reports of OEC tumors, discuss the difficulties of correctly diagnosing them, and examine the possible reasons for their rare incidence. Understanding why OECs rarely form tumors may open avenues for new strategies to combat tumorigenesis in other regions of the nervous system.

Malignant peripheral nerve sheath tumor of the nasal cavity and nasopharynx in a child: A case report

RATIONALE

Malignant peripheral nerve sheath tumors (MPNSTs) are rare neoplasms with only a few reported cases affecting the nasal cavity, paranasal sinuses, and anterior skull base.

PATIENT CONCERNS

A 12-year-old girl with a mass in her nose was admitted to the Department of Otorhinolaryngology of Shenzhen Children's Hospital. She had a 4-month history of progressive, unilateral right nasal obstruction, unilateral mucopurulent rhinorrhea, foul nasal odor, snoring, hyposmia, occasional epistaxis, and no headache, no facial numbness, without eye swelling and vision loss.

DIAGNOSE

A computed tomography (CT) scan of the paranasal sinuses showed a mass (right inflammatory polyp and calcification) involving the nasal cavity, the right maxillary sinusitis, ethmoid sinusitis. There was no nasal septum, orbital, or skull base involvement. On the basis of pathological and immunohistological findings, the tumor was diagnosed as an MPNST with heterogeneous components (cartilage and bone) mesenchymal differentiation after the operation.

INTERVENTIONS

The girl was treated by surgery and chemotherapy.

OUTCOMES

The postoperative course was uneventful. There was no recurrence observed during the 3-year follow-up.

LESSONS

The primary MPNST in the nasal cavity is rare, if nasal neoplasms do not respond well to vasoconstrictors and glucocorticoids in children, the possibility of a tumor should be considered. If new organisms grow rapidly with hemorrhagic necrosis, the possibility of a malignant tumor is greater.

Nasal Cavity and Paranasal Sinuses

The nasal cavity and paranasal sinuses occupy the top of the upper respiratory tract and form pneumatic spaces connected with the atmosphere. They are located immediately beneath the base of the cranium, where crucial vital structures are harbored. From this region, very much exposed to airborne agents, arise some of the more complex and rare benign and malignant lesions seen in humans, whose difficulties in interpretation make this remarkable territory one of the most challenging in the practice of surgical pathology.

Contents of this chapter cover inflammations and infections, polyps and pseudotumors, fungal and midfacial destructive granulomatous lesions, as well as benign, borderline, and malignant neoplasms. Among the neoplasms, emphasis is made on those entities characteristic or even unique for the sinonasal region, such as Schneiderian papillomas, glomangiopericytoma, intestinal- and non-intestinal-type adenocarcinomas, olfactory neuroblastoma, nasal-type NK-/T-cell lymphoma, and teratocarcinosarcoma. Moreover, recently recognized entities involving this territory, i.e., HPV-related non-keratinizing carcinoma, NUT carcinoma, and SMARCB1-deficient basaloid carcinoma, are also discussed in the light of their specific molecular findings. Furthermore, the text is accompanied by numerous classical and recent references, several tables, and 100 illustrations.

An unusual case of schwannomatosis with bilateral maxillary sinus schwannomas and a novel SMARCB1 gene mutation

Schwannomas are benign tumors that arise from Schwann cells in the peripheral nervous system. Patients with multiple schwannomas without signs and symptoms of neurofibromatosis Type 1 or 2 have the rare disease schwannomatosis. Tumors in these patients occur along peripheral nerves throughout the body. Mutations of the SMARCB1 gene have been described as one of the predisposing genetic factors in the development of this disease. This report describes a patient who was observed for 6 years after having undergone removal of 7 schwannomas, including bilateral maxillary sinus schwannomas, a tumor that has not been previously reported. Genetic analysis revealed a novel mutation of c.93G>A in exon 1 of the SMARCB1 gene.

A solitary malignant schwannoma in the choana and nasal septum

Malignant schwannoma is an extremely rare tumor and the risk of malignant schwannoma increases in patients with von Recklinghausen's disease. Recently, we encountered a case of solitary malignant schwannoma in the choana and posterior nasal septum. Malignant schwannoma has not been previously reported in these locations. A 53-year-old man, who was immunologically healthy and showed no abnormal dermatological lesions, presented with a polypoid mass in the right nasal cavity and underwent endoscopic mass excision. The mass originated from the choana and the posterior portion of the right nasal septum. This mass was confirmed as a malignant schwannoma on histological examination and immunohistochemical staining. After endoscopic excision, postoperative adjuvant radiotherapy was administered, and there was no recurrence at 1 year after treatment. This case suggests that a solitary malignant schwannoma should be considered in the differential diagnosis of a mass in the posterior nasal cavity.

Solitary nasal schwannoma clinically presenting as an angiofibroma of the nasopharynx

Benign schwannomas of the nasal cavity are rare. When they do occur, their clinical presentation is variable, and some are fairly vascular. We report the case of a 17-year-old boy who presented with epistaxis associated with a unilateral nasal mass that extended into the nasopharynx. The tumor was removed via a transpalatal approach. In most such cases, a clinical diagnosis of angiofibroma is made. In this case, however, histopathologic examination identified the lesion as a schwannoma.

Nasenhöhle und Nasennebenhöhlen

Die Gesichtsmitte (der Bezirk zwischen Oberlippe und Stirn) entwickelt sich zwischen der 4. und 8. Schwangerschaftswoche. [ 220] Der Stirnfortsatz bildet sich währen der 4. postovulatorischen Woche, aus ihm gehen die oberen und mittleren Anteile des Gesichts hervor. Die Oberkiefer- und Nasenwülste entwickeln sich unterhalb des Stirnfortsatzes. Am Ende der 4. Woche bilden zwei oberflächliche Verdickungen der Nasenwülste die Riechplakoden, die ektodermaler Herkunft sind und aus denen der Epithelbelag der Nasenhöhle und Nasennebenhöhlen hervorgeht. Die Plakoden stülpen sich ein und bilden die Riechgruben, aus denen die vorderen Choanen (Nasenlöcher) und weniger oberflächlich die primitiven hinteren Choanen entstehen. Die medialen Nasen- und Stirnfortsätze bilden das Nasenseptum, die Stirnknochen, Nasenknochen, die Siebbeinzellen- Komplexe und die oberen Schneidezähne. Die lateralen Nasen- und Oberkieferfortsätze vereinigen sich zur Bildung des Philtrum und der Columella. Das knorpelige Nasenskelet bildet sich während der 7. und 8. postovulatorischen Woche tief unterhalb der Nasen- und Stirnbeinknochen aus dem Chondrocranium. Die Nasennebenhöhlen entwickeln sich in der 6. Fetalwoche aus den lateralen Nasenwänden, und ihr Wachstum setzt sich nach der Geburt während des gesamten Kindes- und Jugendalters fort.

[Schwannoma of the nasal cavity: a case report]

Schwannomas of the nasal cavity and paranasal sinuses are quite rare, with 4% occurring in this location. Most of them are benign and do not recur when totally removed by surgery. It is very important to distinguish between schwannoma and primary benign neurofibroma. Neurofibromas are lesions having the possibility for malignant transformation and recurrence. A case of schwannoma in the nasal cavity is reported, and the diagnostic and therapeutic procedures, as well as recommendations from the literature, are described. The histological and immunohistochemical features are discussed in detail to draw a distinction between schwannoma and neurofibroma. In cases of intranasal and paranasal lesions, the existence of a schwannoma must be considered. Differentiating between schwannoma and neurofibroma is important for estimating the risk of malignant transformation and recurrence.

Malignant peripheral nerve sheath tumour of the paranasal sinuses and the anterior skull base

BACKGROUND

Malignant peripheral nerve sheath tumours (MPNSTs) are highly aggressive neoplasms with a marked propensity for local recurrence and metastatic spread. The management of MPNSTs continues to challenge pathologists and surgeons. As MPNSTs of the paranasal sinuses and the skull base are rare, prognostic factors and treatment modalities have not been consistently identified.

PATIENTS AND METHODS

We present a case of MPNST of the anterior skull base and provide an overview of all MPNSTs reported since 1970, in which the tumour location was the anterior skull base or the paranasal sinuses.

RESULTS

Literature review revealed 33 well-documented cases of MPNSTs in this anatomic location. These cases were analysed with emphasis on age, gender, affected site, therapy, outcome, presence of neurofibromatosis, local recurrence and metastases.

CONCLUSIONS

Despite multimodal therapy and advances in surgical techniques, the prognosis of MPNST located in the paranasal sinuses and the anterior skull base remains dismal. Outcome is mainly a function of local control by surgical resection. Adjuvant radiochemotherapy has shown no benefit. It may therefore be advisable to abstain from radiochemotherapy in order to improve chances for surgical intervention in case of recurrent disease. Close follow-up investigations are indispensable.

Description of a neural sheath tumor of the trigeminal nerve: immunohistochemical and electron microscopy study

CONTEXT

Malignant neural sheath tumors of the trigeminal nerve affecting the nasal cavity and the paranasal sinuses are extremely rare. With conventional optical microscopy, their identification is difficult, and it is necessary to confirm them by means of electron microscopy and immunohistochemical techniques.

CASE REPORT

The patient was a 41-year-old woman with a ten-month progressive history of pain followed by painful edema in the left facial region, and with symptoms of bleeding, secretion and nasal obstruction. Studies with imaging methods suggested the presence of an expansive process in the left nasal and paranasal cavities. In the biopsy, the histopathological findings from optical microscopy were suggestive of a tumor of neural origin in the trigeminal nerve. Immunohistochemical and electron microscopy studies confirmed that it was a malignant tumor of the neural sheath of the trigeminal nerve. We describe the clinical, radiological, and histological features of this tumor and review the literature.

Free Rectus Abdominis Myocutaneous Flap With Anterior Rectus Sheath to Provide the Orbital Support in Globe-Sparing Total Maxillectomy

Reconstruction after total maxillectomy with preservation of the orbital contents is technically more challenging than when the maxillectomy is combined with orbital exenteration. It results in severe complications if the orbital content is not supported. We would like to introduce a new technique using free rectus abdominis myocutaneous (RAM) flap with anterior rectus sheath to support the orbital content in a patient who underwent globe-sparing total maxillectomy. The large resection of the recurrent maxillary peripheral nerve sheath tumor was performed in a 34-year-old male patient. Right free RAM flap was harvested simultaneously with the tumor resection. The anterior sheath of upper portion of the rectus muscle was also incorporated into the flap. The free edge of the upper anterior rectus sheath was anchored to three different points: Lateral rim, medial rim and the posterior remnant of the bony orbital floor with non-absorbable suture. Consequently, orbital support was achieved with well-vascularized, thin, strong fascia with smooth surface. Right facial artery and vein were chosen as recipient vessel. Duration of the operation was 5.5 hours. Postoperative period was uneventful. Six months after the surgery, the right eye was in good position without inferior dystopia. Eyeball movement could be done without restriction. The patient also denied diplopia. Reconstruction of globe-sparing total maxillectomy defects with free RAM flap with anterior rectus sheath has several advantages that enable the reconstructive surgeon to solve the multiple complex reconstructive task with one flap: 1) elimination of the secondary donor site morbidity; 2) more simply addressing the challenging task of the eye support than the other techniques; 3) obliterating the maxillectomy defect and closing the palate; 4) restoring the large skin defect; and 5) reducing the operation time. It is difficult to conclude that this technique is the best choice in such cases based on a report of the single case. However, presented technique should be kept in mind as a practical and effective reconstructive option in cases that have underwent the total maxillectomy with the preservation of the orbit.

Primary malignant schwannoma of the cervical plexus with melanocytic differentiation

Primary malignant schwannomas are rare neoplasms of nerve sheath origin, especially in the location of the head and neck where few cases are described in the literature. These tumours may pose a diagnostic dilemma in the work-up of a neck mass. The case presented here is of a malignant schwannoma that originated in the cervical plexus with the rare histological feature of melanocytic differentiation. Histopathological examination with immunostaining techniques is essential for the diagnosis of these tumours. The management of these neoplasms is still controversial, although the treatment of choice is radical surgical excision of the lesion. The role of postoperative radiotherapy or chemotherapy is not clear, although some authors recommend its use to prevent local recurrence, for unresectable recurrent tumours or in cases of distant metastases.

Epithelioid malignant peripheral nerve sheath tumor involving maxillary sinus

We present a case of epithelioid malignant peripheral nerve sheath tumor (MPNST) located in the maxillary sinus region in a young man. The clinical history was short, but at admission the neoplastic infiltration was so extensive that only diagnostic biopsy was performed. The patient received palliative treatment and died 6 months later. Histologically, the neoplasm had a predominant epithelioid component. Neoplastic tissue was vimentin, S-100, Cam 5.2 and neuron-specific enolase positive. P53 protein reaction was found in 6% of the cells and the proliferation index assessed with Ki-67 was 52%. An appropriate immunohistochemical panel was essential for the final diagnosis of this epithelioid malignant tumor, with the location rather unusual for MPNST.

Spinal Cord Metastasis of a Non-neurofibromatosis Type-1 Malignant Peripheral Nerve Sheath Tumor: An Unusual Manifestation of a Rare Tumor

Malignant peripheral nerve sheath tumors are rare spindle-cell sarcomas derived from Schwann cells or pluripotent cells of the neural crest. They arise from the spinal roots, peripheral nerves, brachial and lumbosacral plexi, cranial nerves and terminal nerve fibers within soft tissue, intestine, lung and bone. These tumors recur either locally, or metastasize distally. Most of these tumors occur in association with neurofibromatosis type 1. Spinal cord metastasis from malignant nerve sheath tumors associated with neurofibromatosis type 1 is very rare. We describe a rare case of near-total spinal cord metastasis in a patient with malignant nerve sheath tumor in the absence of neurofibromatosis, and highlight the microscopic findings and natural history of this disease process.