TITLE: TRACHEAL SCHWANNOMA: AN UNCOMMON ENTITY
Abstract:
Primary tracheal tumours are extremely rare with most of them being malignant. Primary tracheal tumours are histologically similar but 100 times less common than main stem tumours. Primary neurogenic tumours of trachea account for only about 9% of all neoplasms of trachea. Tracheal schwannoma is among the rarest of them and there is no unanimity of opinion regarding its treatment.
They are usually seen in females and their clinical features are not specific. Chronic cough,
progressive respiratory distress and even asthma-like conditions prevail as presenting symptoms
and signs.
Key words: tracheal, schwannoma, bronchscopy
CASE REPORT:
CHIEF COMPLAINTS:
A 34 year old lady presented with breathlessness for 11/2 year, cough with expectoration for 5 months, 2 episodes of hemoptysis 3 months back, pain in right side of chest for 2 months.
Initially the patient could walk for more than a mile without any problem but gradually the distance decreased and this was associated with breathlessness. There was more problem walking uphill/ staircase. For past 5 months, the patient also started having cough which was initially dry but later changed to productive cough. Expectoration was mucoid with on/ off purulent. She also, sometimes coughed out inspissated dry phlegm. 3 months back, she had 2 episodes of hemoptysis 1 week apart. She was admitted and thoroughly investigated. HRCT chest revealed a large endobronchial growth involving lower trachea and right main bronchus with distally collapsed lung. Cardiomediastinum and trachea shifted to right side. Multiple enlarged pretracheal, right paratracheal and right hilar lymph nodes were noted with no necrosis: max 1.6 cm. Bronchoscopy revealed a huge mass with necrotic slough at origin of right main bronchus.
SURGERY: Patient was placed in lateral decubitus position; right posterolateral thoracotomy was done in 4th intercostal space. Tumor had widened the tracheal diameter to approximately 5cm and the tumor had extended from carina to right main bronchus. Trachea was cut at carinal level. Tumor along with a sleeve of trachea was excised with adequate margins. Tumor polypoidal in nature. Pneumonectomy was completed. Trachea was closed in two layers with prolene 5 0 and buttressed with a pleural patch.
Discussion
Primary tracheal schwannoma is an uncommon entity with a prevalence of < 0.5% of all tracheal tumours. Two thirds of all primary tracheal tumours are evenly divided between squamous cell carcinoma and adenoid cystic carcinoma [1]. The remaining one third is a heterogeneous group composed of malignant, intermediate, and benign lesions.
The first reported case of neurogenic intrapulmonary tumor was in 1914 by Askanazy[2]. These are more commonly seen in women with no age predilection with male to female ratio being 1:3.
Its clinical presentation is non-specific. Chronic cough, progressive respiratory distress and asthma-like conditions are usual complaints. Suboptimal response to inhaled drugs or appearance of flow loop volume in PFT leads to the need of further investigation. Unfortunately, an average delay of 10-15 months in the diagnosis is reported[3]. The most important and preferred modality for diagnosis is rigid bronchoscopy, because it assesses the extent of the lesion and the length of healthy trachea available for anastomosis. It also provides accurate measurements than the flexible bronchoscopy and gives the advantage of better control of the obstructed airway and control of any bleeding that may occur following biopsy. Bronchoscopy reveals a solitary, well encapsulated mass arising most often from the posterior tracheal wall; the lower third of the trachea is the most common site followed by the upper and then the middle thirds[4]. Computerized Tomography scan typically shows a well circumscribed enhancing mass within the tracheal lumen with no specific features. MRI of a tracheal schwannoma displays isointense or hyperintense T1-weighted images and hyperintense T2-weighted images with heterogeneous enhancement.
The diagnosis of tracheal schwannomas is primarily pathological. Grossly, they are well
circumscribed and encapsulated; microscopically, areas of fibrillary, intensely polar, elongated appearing tissue type with high cellularity (Antoni A areas) as well as areas loose microcystic myxoid fashion (Antoni B areas) are appreciated. Antoni A areas are punctuated by nuclei arranged in stacked alignments known as palisades which are called Verocay bodies. However, these Verocay bodies are not pathognomic of schwannoma. No capsular invasion, nuclear pleomorphism or mitoses is present.
Although not entirely specific, S-100 protein is a reliable marker for the diagnosis of schwannomas and is typically seen in the Antoni A areas. Immunohistochemical stains for
glial fibrillary acidic protein (GFAP), neurofilament protein and vimentin can also be positive[5]. The differential diagnosis of spindle cell lesions of the larynx and trachea includes spindle cell carcinoma, and wide range of benign and malignant mesenchymal lesions. Malignant lesions
include a number of spindle cell sarcomas such as fibrosarcoma, synovial sarcoma, and leiomyosarcoma; however, these are extremely rare in this location and do not arise from the surface epithelium
Tracheal neurofibroma has uncommonly been associated with neurofibromatosis type I, however literature shows no association with schwannoma. Chondromas, papillomas, neurofibromas are benign tumours of trachea in the order of prevalence. The site of the lesion is variable and has been found as low down as the lingular bronchus.
Schwannomas bring symptoms when the tumor grows to obstruct the tracheobronchial lumen. These symptoms are late as they are slow growing in nature.
The rarity of such lesions has resulted in the paucity of consensus on standard surgical techniques but the primary treatment is surgical excision. Bronchoscopic excision, sleeve excision or tracheal resection, are all commonly accepted treatment modalities[6].
Surgical excision can either be done bronchoscopically, limited resection of the trachea with lung preservation or pneumonectomy upto the carina when the tumor has reached upto carina and long term obstructive collapse has damaged the lung. Bronchoscopic resection when done adequately shows no recurrence in the 5 years follow up period. Late recurrences have been seen upto 12 years[7]. Laser resection with CO2 or Nd- YAG laser seems to be effective treatment for pedunculated tumours without the extratracheal extension. Tracheal resection with reconstruction has been more advocated for sessile lesions with or without an extra-tracheal component.
Benign tumours of trachea are classified based on their origin:
• Neural: carcinoid, benign clear cell, neurofibroma, myoblastoma.
• Epithelial: papilloma, chondroma, lipoma, fibroma, fibrous histiocytoma.
• Mesenchymal: hamartoma
Neurogenic tumor can be schwannoma or neurofibroma. Primary neurogenic tumor are usually found in lungs and bronchi. These are highly uncommon in upper respiratory tract.
Neurofibroma has not been reported in women.
Schwannoma of the trachea arises from intra-luminal neurogenous tissue- Schwann cells of the nerve sheath. These tumours typically are single, well circumscribed, encapsulated tumours attached to a nerve but does not contain an axon.
Schwannomas are rarely associated with von- Recklinghausen disease, and rarely undergo malignant changes. Neurofibromas, on the contrary, are usually multiple and more commonly associated with von-Recklinghausen disease. Neurofibroma shows proliferation of all neural tissues including Schwann cells, perineural cells and nerve axons. They may go under malignant changes.
References:
1. Grillo HC, Mathisen DJ. Primary tracheal tumours: treatment and results. Ann Thorac Surg 1990;49:69-77.
2. Roviaro G, Montorsi M, Varoli F, et al.Primary pulmonary tumours of neurogenic origin. Thorax 1983;38:942-945.
3. Marc S. Karlan, M.D., Peter A. Livingston, M.D., Daniel C. Baker, Jr., M.D. Annals of Otology, Rhinology & Laryngology. Vol 82, Issue 6, pp. 790 – 799.
4. Rusch VW, Schmidt RA: Tracheal schwannoma: management by endoscopic laser resection. Thorax; 1994, 49:85-86.
5. Schwannoma – Surgical Pathology Criteria – Stanford University School of Medicine.
6. Tracheal schwannoma: a misleading entity Hamdan, Abdul Latif Moukarbel, Roger V. Tawil, Ayman El Khatib, Mohamad Hadi, Ussama Middle East Journal of Anesthesiology 2010; 20 (4): 611-613.
7. Righini CA, Lequeux T, Laverierre MH, Reyt E. Primary tracheal schwannoma: One case report and a literature review. Eur Arch Otorhinolaryngol 2005;262:157‑60.