Endoscopic Excision of Primary Tracheal Schwannoma: A Case Report

Background

Primary tumors of the trachea are commonly malignant. Squamous cell carcinoma and adenoid cystic carcinoma are the most common and account for 75% of cases. The remaining 25% are tumors of multiple histological subtypes, including benign, intermediate, and malignant tumors. Among them is a rare tumor, primary tracheal schwannoma [1], which is considered a neurogenic tumor, including schwannoma and neurofibroma. In its early stage, this tumor presents with non-specific symptoms, and asthma is sometimes misdiagnosed. However, as it grows, it presents with obstructive symptoms of the tracheal lumen. This tumor was managed by open re-section surgery until recently, when endoscopic excision began being used [1–4]. We present a rare case of primary tracheal schwannoma that was managed by endoscopic excision.

Case Report

A 37-year-old man was referred to our clinic by our thoracic surgery colleagues. The patient had progressive shortness of breath and a wheezy chest that started 3 months prior to presentation. There was no associated history of dysphonia or dysphagia. The patient was seen in another local hospital, where asthma was diagnosed and treated accordingly. He reported temporary improvement with the usage of bronchodilator medication. The patient was a lifelong nonsmoker. He had no medical or surgical history and was not on any regular medications. The family history was unremarkable, with no history of cancer. The patient was single and working in the food industry.

The patient was admitted to the hospital. Lung auscultation revealed a prolonged expiratory phase and wheezing over the cervical trachea in the expiratory phase. Multiplanar reconstructions and a contrast-enhanced computed tomography (CT) scan showed a well-defined rounded, solid intraluminal tracheal mass at the proximal segment (at the level of the thoracic inlet). It had homogeneous density and was enhanced by the contrast agent. It was adherent to the right tracheal wall and measured 17×19×22 mm in maximum mediolateral, anteroposterior, and circumferential dimensions, respectively. There was no extratracheal extension and no enlarged cervical lymph nodes (Figure 1A–1C). Prior to the surgical management, flexible bronchoscopy was done, showing a round, smooth surface, and tan-colored mass in the proximal part of the trachea. It was 3 cm distal from the vocal cords, almost 2 cm in maximum diameter, and occluding approximately 90% of the tracheal lumen (Figure 1D). Discussion between the anesthetist, thoracic surgeon, and head and neck surgeon was done for the surgical plan. A difficult airway was anticipated in our patient, as the trachea was found to be nearly completely occluded by the tumor. The plan was to proceed with fiberoptic intubation and perform an awake tracheostomy if it failed. The airway was secured by awake tracheostomy, as the fiberoptic intubation was unsuccessful. Given that the mass was in the cervical trachea opposite the second, third, and fourth tracheal ring, low tracheostomy was done in the fifth tracheal ring, where a horizontal incision was made and endotracheal tube size 7 was cuffed, inserted, and secured. The patient then underwent endoscopic excision of the mass. Bronchoscopy was used for the operation. A sickle knife, micro scissor, and suction diathermy were used where incision, stripping, and hemostasis were done through the tumor pedicle (Figure 2A, 2B). After the tumor was removed completely, the tracheostomy was closed, and endotracheal intubation was done in the same sitting. Postoperatively, the patient was kept in the Intensive Care Unit for 24 h and extubated there. Immediately after extubation, the patient reported improvement in the shortness of breath. On postoperative day 3, the patient was discharged home. The first postoperative visit after 2 weeks showed subjective improvement in preoperative symptoms, and the flexible bronchoscope showed a completely healed surgical site, with a patent airway.

Histopathological examination of the mass showed spindle cells with elongated palisading nuclei, representing an Antoni A growth pattern, negative for increased mitotic activity or necrosis. The tumor demonstrated diffuse and strong nuclear and cytoplasmic positivity of S-100 protein (Figure 3A, 3B). Both the histopathological examination and immunohistochemistry confirmed the diagnosis of primary tracheal schwannoma.

Discussion

Primary neurogenic tumors of the trachea, which include schwannoma, are rare. Schwannoma arises from the peripheral nerve sheath; it is less common than neurofibroma [5]. Between 2015 and 2022, 10 cases of primary tracheal schwannoma were reported in English-language literature [3,4,6–9]. It is a benign tumor that is more commonly seen in the distal one-third of the trachea, followed by the upper one-third and then the middle one-third of the trachea [2]. The cause of its development is unknown. It is rarely associated with von Recklinghausen disease [10].

Primary tracheal schwannoma is a slowly growing tumor commonly seen in young adults, with a female predilection. Its clinical presentation depends on the site, size, extent of the tumor, and degree of airway obstruction [11]. In the early stage of the tumor, most patients reported coughing, wheezing, and dyspnea and were misdiagnosed as having asthma and treated accordingly [12]. This led to the delay of diagnosis and more severe airway symptoms, which were reported to be 17 months on average from the onset of symptoms [2].

Imaging plays a significant role in diagnosing tracheal tumors and surgical planning. A chest X-ray is not helpful in this context, as it is normal in up to 75% of cases [4]. CT of the chest is the main imaging that can evaluate the presence of a mass, its location, size, the degree of airway obstruction, and if there is an extra tracheal extension. Magnetic resonance imaging (MRI) is superior for imaging the trachea, especially when assessing the extratracheal extension. However, based on the reported literature, MRI did not add more information, and the chest CT was enough for this evaluation [13]. For further evaluation, flexible bronchoscopy is used to visualize the mass, and a biopsy can be taken [14]. To confirm the diagnosis of schwannoma, an immunohistochemical analysis must reveal diffuse positivity of S-100 protein and vimentin [15].

In patients presenting with obstructive symptoms, comprehensive multidisciplinary perioperative airway management is critical for effective treatment and uneventful outcomes. Most of the national guidelines for the management of difficult airways recommend methods that maintain spontaneous respiration while trying to secure a definitive airway. These methods mainly include awake tracheal intubation or awake tracheostomy [16]. In our case, fiberoptic intubation failed, and further intubation attempts can cause bleeding and fragmentation of the tumor. Consequently, an awake tracheostomy was chosen to secure the airway.

The criterion standard management of tracheal schwannoma is open surgical tracheal resection with end-to-end anastomosis.

However, it is not suitable for long segmental tracheal resection [17]. Reports of the use of endoscopic excision of this tumor have increased in recent literature [3]. The endoscopic approach includes laser resection, electrocautery snaring, argon plasma coagulation, cryotherapy, endoscopic excision, microdebridement, and high frequency gamma knife [2,3]. Chen et al [18] described a different approach using video-assisted thoracoscopic window resection with a good postoperative outcome. However, it was limited to tracheal tumors occupying less than one-third of the tracheal circumference and less than 1.5 cm in the vertical dimension.

The choice of open surgical vs endoscopic management of tracheal schwannoma is influenced by the size of the tumor, pedicle of the tumor (sessile vs pedunculated mass), extra tracheal component, and cardiopulmonary function of the patient. Endoscopic management is indicated when the tumor size is up to 2 cm, it is a pedunculated mass, there is no extra tracheal extension, or the patient has poor cardiopulmonary function [2,19]. We believe that successful endoscopic removal depends on appropriate tumor visualization and the ability to remove the tumor with an adequate margin. This applied to the present case, which met the criteria to be managed endoscopically, as the tumor was pedunculated with a clear base, completely within the trachea, and less than 2 cm.

Although endoscopic management is superior to open surgical management in terms of reducing complications, operative time, and patient recovery period, recurrence after endoscopic excision is an issue. In our case, the follow-up period was short, but as reported by Sharma et al [5] and Gibb et al [20], postoperative bronchoscopic surveillance showed no recurrence in 8 and 18 months, respectively.

On the other hand, Ge et al [2] found recurrence by bronchoscopic examination 2 weeks after endoscopic excision, which was managed by open surgical excision. We believe this early recurrence can be attributed to an incomplete excision of the mass, according to their report, in which 75% of the mass was excised by the endoscopic technique [2]. Once recurrence of this tumor occurs, the choice of open surgical tracheal re-section becomes absolute. The onset of recurrence is variable, and 1 case reported late recurrence 12 years after endoscopic excision [1]. Given this fact and the slow-growing nature of the tumor, it is preferable to have annual imaging, including CT chest, magnetic resonance, or positron emission, to detect recurrence, or to perform imaging when the patient becomes symptomatic again. Other modalities include bronchoscopic surveillance for recurrence detection [1,4].

The general prognosis of primary tracheal schwannoma managed surgically or endoscopically is excellent [6].

Conclusions

Primary tracheal schwannoma is rare. Imaging, including chest CT or MRI, needs to be considered once upper respiratory symptoms are persistent. Endoscopic excision is an excellent option for primary tracheal schwannoma with no extra tracheal extension, up to 2 cm in size, and pedunculated mass. Patients need to be appropriately selected to avoid recurrence.