The Varied Presentations of Sinonasal Region Schwannomas: Apropos of Four Cases

Abstract

Schwannomas of the sinonasal compartment are rare benign neoplasms of peripheral nerve sheath origin and constitute ~ 4% of all head and neck schwannomas. The presentation may simulate a range of benign and intermediate grade pathologies. Management involves surgical excision via open or endoscopic approach. To describe the clinico-epidemiological characteristics and surgical outcomes in sinonasal region schwannoma patients operated at our institute. The study is a descriptive case series of patients with sinonasal region schwannomas treated at our institution. A retrospective search of electronic database of the Department of ENT and Head and Neck Surgeries and Department of Pathology was conducted from January 2013 to January 2019. The various demographic and clinical details of the patients were extracted. A total of four patients operated for sinonasal region schwannoma were identified. The involved sites were nasal dorsum, nasal cavity, pterygopalatine fossa and infratemporal fossa. The mild, non-specific symptoms resulted in patients ignoring their symptoms for a while initially and presenting late. The nasal dorsum lesion was revealed as a surprise during open rhinoplasty for correction of nasal deformity. Complete excision was achieved in all the cases and no recurrence has been noticed during the follow up (varying from 6 months to 6 years) till date. The diverse clinical manifestations and approaches to the treatment of schwannomas in this specific region are discussed. The surgical excision is the standard of care in dealing with these neoplasms. This series highlights the rarity of this pathology in the sinonasal area, diagnostic surprises and the decision making to choose the correct surgical approach for complete excision. Once excised completely, recurrence is not expected.

Introduction

Schwannomas are benign neoplasms arising from the Schwann cells of peripheral nerve sheaths. Head and neck involvement occurs in 25–40% of total cases. Among the extracranial head and neck subsites, the commonest location of origin is in the neck, with the tumors arising from the cervical sympathetic chain and vagal nerve. Sinonasal schwannomas constitute around 4% of the total head and neck schwannomas and have been reported in either case reports or small case series [1].

In view of limited information available regarding these tumors, it is desirable to add more patients to the literature to understand the clinicopathological characteristics of the tumor and surgical outcomes. The complex sinonasal anatomy makes the early detection of tumors difficult unless the tumor is visible in the anterior nasal cavity or causing early nasal obstruction by blocking the respiratory passage of the nose. We present our experience of treating four cases, presenting in the sinonasal region, with their varied symptomatology and surgical approaches for tumor removal.

Materials and Methods

We carried out an electronic database search of the patient records (January 2013 to January 2019) from the Department of Pathology and Department of ENT and Head and Neck Surgeries at our institution to identify the patients operated for schwannomas presenting in the sinonasal region. The retrospective chart review of the clinico-epidemiological characteristics and management details of the patients was performed. The parameters extracted from the chart review included the patient age, gender, presenting symptomatology, examination findings, investigations performed, surgical approaches undertaken and the follow up information. Only the patients with available histopathology and complete inpatient and follow up information were included for review. For follow up, the data from the outpatient follow up visits was recorded and the follow up was carried out using clinical and (when applicable) radiological investigations. The patient consent was taken for the use of medical photography and case details, however, no patient personal identifiers were disclosed. Approval from the institutional ethical committee was obtained (Reference No. MICR: 993/2019 {Academic}) for the study.

Results

A total of four patients operated for sinonasal region schwannoma were identified. The involved sites were nasal dorsum, nasal cavity, pterygopalatine fossa and infratemporal fossa. The mild, non-specific symptoms resulted in patients ignoring their symptoms for a while initially and presenting late. The nasal dorsum lesion was revealed as a surprise during open rhinoplasty for correction of nasal deformity. Complete excision was achieved in all the cases and no recurrence has been noticed during the follow up (varying from 6 months to 6 years) till date. The description of the individual patients is detailed below.

Case 1

A 28-year-old female presented to us with the complaint of non-progressive external nose deformity noted for the last 4 years. There was no history of trauma, nasal pain, obstruction or discharge. On examination, the nasal tip and right nasal dorsum were found to be soft and bulbous (Fig. 1a). Nasal endoscopy showed normal findings. The patient was taken up for correction of the deformity via an open rhinoplasty approach under general anesthesia. During dissection of the nasal dorsum soft tissue, an encapsulated, cystic swelling was found in between the right upper and lower lateral cartilages (Fig. 1b). The swelling was removed in toto and sent for histopathological examination. A piece of cartilage was taken from nasal septum to fill the defect and camouflage the concavity over upper lateral cartilage. The histopathological examination revealed the lesion to be a well-encapsulated schwannoma with cystic degeneration (Fig. 1c, d). The patient had a satisfactory post-operative cosmetic and functional outcome and is disease free at a follow up of 3 years.

Fig. 1.

a Fullness over the right side of nasal dorsum without discrete visible or palpable swelling. b Intraoperative view showing well defined swelling with a smooth surface (*). c Light microscopic view showing typical findings of schwannoma, with cellular Antony ‘A’ areas (lower half of the slide) and scantly cellular Antony ‘B’ areas (upper half of the slide) (H&E stain; original magnification ×100). d Immunohistochemistry picture showing a uniform and dense staining with S-100 (original magnification ×100)

Case 2

A 13-year-old female patient was admitted with a 6 months’ history of right sided nasal blockage which had worsened over last 1 month. Nasal endoscopy showed a pale greyish soft polypoidal mass in the posterior part of right side nasal cavity (Fig. 1d) and a recent computed tomography (CT) scan performed at another center revealed an expansile soft tissue lesion involving right sphenoid sinus and nasal cavity, pushing the inferior and middle turbinates laterally. No intra lesion ossification and calcification were seen. There was no evidence of bone erosion or intracranial/intraorbital extension. The septum was pushed to the opposite side. Complete opacification was noted in the left posterior ethmoid air cells albeit with preserved bony septae (Fig. 2a–c).

Fig. 2.

Non contrast CT scan of the paranasal sinuses, a coronal, b sagittal, c axial cuts, showing homogenous expansile soft tissue density involving right nasal cavity, posterior ethmoids and sphenoid sinus. There is no bony erosion, destruction or intraorbital/intracranial extension. d Endoscopic view of the right nasal cavity showing mucosa covered, pale, globular lesion (*) between the septum and lateral nasal wall. e Intraoperative view showing the piecemeal removal of the moderately vascular tumor. f Showing the tumor pedicle (arrow) attached to the posterior part of the right side of the nasal septum. The sphenoid sinus ostium was found to be widened by the tumor projecting into the anterior part of the sinus. Rest of the sphenoid sinus was found to be filled with thick mucoid secretions

The patient was taken up for functional endoscopic sinus surgery under general anesthesia. Intraoperatively, the mass was found to be mucosa covered, filling the right nasal cavity, choana and anterior part of the right sphenoid sinus, and pedicled over the posterior nasal septum (Fig. 2f). The right maxillary sinus and part of the sphenoid sinus was filled with thick mucoid secretions. Mass was removed completely in a piecemeal fashion using debrider and send for histopathological examination. The histology showed features typical of schwannoma. At the last follow up 6 months’ post-surgery, there was no sign of recurrence. The patient has nasal dryness without crusting, for which saline nasal douching were advised.

Case 3

A 24-year-old male presented with complaints of heaviness over the left side of the face. Diagnostic nasal endoscopy showed no abnormality. Magnetic resonance imaging (MRI) of the face and neck showed a well-circumscribed mass lesion, around 2.2 × 2.3 × 2 cm with areas of cystic degeneration, involving left retro maxillary fat with anterior bowing of posterior wall of maxillary sinus without any evidence of bone destruction. On contrast administration, the lesion showed heterogeneous enhancement (Fig. 3a, b). The tumor was removed completely in a piecemeal fashion via transnasal transmaxillary endoscopic approach under general anesthesia (Fig. 3c, d). The histology was diagnostic of schwannoma. The last follow up with contrast-enhanced CT scan performed at 18 months’ post-surgery showed no evidence of recurrence.

Fig. 3.

Magnetic resonance imaging, a contrast enhanced, T1 weighted sequence, showing the well-defined, round, heterogeneously enhancing tumor mass (arrow) involving the left pterygopalatine fossa, pushing the posterior wall of the maxilla anteriorly, b T2 weighted sequence, showing the intermittent areas of hyperintensity suggestive of cystic degeneration present inside the tumor mass. c Endoscopic view of the posterior wall bulge of the left maxillary sinus seen through a wide maxillary antrostomy using a 30° rigid endoscope. d The tumor exposed after removal of the posterior wall of the maxilla

Case 4

A 37-year-old male presented to us with the complaint of gradually progressive decreased mouth opening. There was no history of pain, facial swelling, fever, dysphagia, dyspnea or trauma. On local examination, trismus was present with a mouth opening of one fingerbreadth. Rest of the ear, nose, throat, face and neck examination was within normal limits. Laryngoscopy showed normal findings.

A Contrast Enhanced MRI was obtained which showed a well-defined round mass approximately 4.4 × 3.6 × 4.3 cm in size involving left infratemporal fossa, abutting medial aspect of the mandibular ramus and showing no significant marrow edema (Fig. 4a, b). Superiorly, the mass was reaching up to skull base without any bony destruction or intracranial extension (Fig. 4c). On the basis of the above findings, a possibility of slow-growing neoplastic lesion was considered. CT guided biopsy was obtained but was inconclusive.

Fig. 4.

Magnetic resonance imaging, a axial, T1 weighted image without contrast, showing an isointense, globular, well-defined tumor involving the left infratemporal fossa. b Post contrast administration, the tumor shows smooth peripheral rim contrast enhancement with a few small internal enhancing foci. c Coronal view, T2 weighted image showing predominantly hypointense tumor with peripheral hyperintense incomplete rim along with internal small, ill-defined T2 hyperintense foci. d Light microscopic image showing spindle cells with hypo and hypercellular areas with focal palisading and Verocay body formation (arrows) (H&E stain; original magnification ×100). e Immunohistochemistry showing intense staining with S-100 (original magnification ×100)

The patient was undertaken for surgical excision of the mass lesion under general anesthesia. Via maxillary swing approach, a well-circumscribed, well encapsulated tumour was removed from infratemporal fossa in toto. The nerve of origin could not be identified intraoperatively.

Histopathological examination revealed an ancient schwannoma, with typical ‘Antony A’ and ‘Antony B’ areas with a strong immunopositivity for S-100 (Fig. 4d, e). Intensive mouth opening exercises were advised and the mouth opening of the patient stabilized at two fingerbreadths at 1 year. The patient was followed up for 6 years with regular visits every 6 months to 1 year, with no signs of recurrence.

Discussion

In the sinonasal region, probable source of origin of the schwannomas is from the sensory branches of the trigeminal nerve or from the small autonomic nerve branches supplying the glandular and vascular structures of the sinonasal region. Unlike schwannomas arising from other body sites, the schwannomas originating inside the nose and paranasal sinuses frequently lack capsule. This lack of peritumoral capsule is probably related to their origin from the autonomic nerve fibers lacking perineural cells involved in the formation of the peritumoral sheath (in analogy with the gastric schwannomas) [2]. However, the schwannomas arising from the trigeminal nerve division (as in cases with orbital, pterygopalatine fossa {PPF} and infratemporal fossa {ITF} schwannomas), tend to have a well-defined tumor capsule. The lack of capsule, however, does not seem to affect the biological behavior of the tumor, as the recurrence rate does not appear to differ significantly from the encapsulated counterparts after complete excision [3]. Our cohort of the patients demonstrates the diverse ways in which the schwannomas of the sinonasal territory can manifest. Except for the patient with nasal septal schwannoma, all our patients (nasal dorsum, PPF and ITF schwannomas) had a well-defined capsule.

Nasal septal schwannomas tend to arise predominantly from the posterior part of the nasal cavity, probably from the posterior septal nerve [4]. The tumor tends to push the nerve to the periphery, which in cases of sinonasal tumors, becomes difficult to discern, making the nerve preservation unrealistic.

The tumor confined to the sinonasal cavity may be confused with nasal polyp based on limited visualization of the surface characteristic of the tumor projecting in the nasal cavity. The conventionally applied imaging modality in case of typical sinonasal polyposis (non-contrast computed tomography) may not reliably reveal the tumor characteristics, and a contrast CT or MRI should be utilized for better characterization. The slow growth pattern of this benign lesion tends to cause bone remodeling without significant bony destruction. T2 weighted MRI sequences may suggest a neurogenic origin of the tumor by revealing the target sign (peripheral hyper and central hypodense areas, representing the ‘Antony B’ and ‘Antony A’ areas, respectively) and fascicular sign (multiple ring like areas representing the nerve fascicles histopathologically) [5, 6]. This distinction of the thickened secretions from the tumor can be best performed with a contrast-enhanced MRI scan. Tumor in patient number ‘2’ (section 2.1.2, case 2; described above and in Table 1) in our series appeared to involve the entire sphenoid sinus on preoperative imaging, however, the opacification of the sphenoid sinus was intraoperatively found to be due to the accumulation of the secretions.

Table 1.

Presentation and management details of the patients with sinonasal region schwannomas in our series

SN	Age (years)/gender	Location	Presenting symptoms	Duration of symptoms	Surgical approach	Follow up duration	Follow up outcome
1	28/female	Nasal dorsum	External nasal deformity	4 years	Open rhinoplasty	3 years	No recurrence
2	13/female	Right nasal cavity and sphenoid sinus (posterior nasal septum)	Right side nasal blockage	6 months	Endoscopic sinus surgery	6 months	No recurrence. Nasal dryness managed conservatively
3	24/male	Left pterygopalatine fossa	Heaviness over left side of the face	1 year	Endoscopic sinus surgery	18 months	No recurrence
4	37/male	Left infratemporal fossa	Decrease mouth opening	18 months	Maxillary swing	6 years	No recurrence

Definite diagnosis of the tumor is possible only on histopathology. Under light microscopy, the spindle cells with elongated, wavy nuclei and abundant eosinophilic cytoplasm, are distributed in biphasic pattern with highly cellular areas having the spindle cells arranged in palisades, constituting ‘Antony A’ areas, alternating with hypocellular areas with myxoid matrix having loosely arranged, scattered spindle cells, forming ‘Antony B’ areas. Sinonasal schwannomas tend to be highly cellular with the predominance of ‘Antony A’ areas. The hypercellularity of the tumors, however, does not increase the biological aggressiveness, risk of malignancy or tumor recurrence.

Surgical excision is the treatment of choice for these lesions. Surgical approaches to these tumors are dependent on the site and extent of tumor. Depending on the location and accessibility, either an open or endoscopic approach may be employed. For the lesions confined to sinuses and the nasal cavity, endoscopic sinus surgery (ESS) is the standard of treatment. With the technical and technological advancement, there is a general trend towards adopting endoscopic approaches even for larger lesions previously considered unsuitable for endoscopic approaches. However, endoscopic visualization and accessibility may be severely hampered for the lesions located far anteriorly (erosion of the nasal bone, frontal sinus anterior wall) or far laterally (tumor with origin beyond the mid pupillary line in the lateral part of the frontal sinus, the involvement of soft tissue of the cheek) [7]. Lesions crossing the major vessels, though, can be approached endoscopically, are more safely dealt with after gaining vascular control via an external approach. In toto removal of the massive lesions via endoscopic approaches is impractical, and piecemeal excision of the tumor is the accepted strategy for removal of these tumors, without incurring a higher recurrence risk [8]. In two of our patients (case 2 and 3; section 2.1.2 and 2.1.3 above), the tumor could be completely removed endoscopically, while the involvement of nasal dorsum and ITF were managed via open approaches, without any recurrences noted during follow up.

Conclusion

Sinonasal schwannomas can present with a variety of non-specific presentations and may present as an unexpected finding as in our patient undertaken for rhinoplasty. Based on the clinico-radiological appearance, it is usually not possible to make a reliable decisive diagnosis preoperatively. The definitive diagnosis is possible only on histopathology, though imaging can provide some clues towards the neurogenic origin of the tumor. Complete surgical excision is the treatment of choice and leaves no room for recurrence. The realm of the endoscopic approaches to the sinonasal and adjoining compartments is expanding, and the majority of these tumors can be removed in a piecemeal fashion satisfactorily without an increase in the incidence of recurrence.

Funding

This research did not receive any specific Grant from funding agencies in the public, commercial, or not-for-profit sectors.

Compliance with Ethical Standards

Conflict of interest

All authors declare that they have no conflict of interest.

Ethical Approval

This work was done at Medanta—The Medicity, Gurugram, Haryana, India. Approval from the institutional ethical committee was obtained (Reference No. MICR: 993/2019 {Academic}) for the study.

Human and Animal Rights

Research involving human participants and/or animals: retrospective study; study approved and consent waved by Institutional Ethical Committee.

Informed/Written Consent

Informed/written consent was obtained from the individuals participating in the study.