Endobronchial schwannomas are rare and often benign neoplasms that develop from the nerve sheath of the peripheral nervous system. We report a case of a solitary right-sided endobronchial schwannoma presenting with progressive respiratory symptoms. We discuss the clinical features of the disease, histopathological manifestations, diagnostic considerations, and therapeutic options.
A 61-year-old man was referred to our pulmonary clinic for evaluation of dyspnea and wheezing. He complained of mild dyspnea at rest, wheezing in the supine position, and intermittent nonproductive nocturnal cough, progressing over the previous 4 months. He denied chest pain, orthopnea, paroxysmal nocturnal dyspnea, palpitations, hemoptysis, fever, chills, sweats, and gastroesophageal reflux.
The patient’s past medical history included hepatitis B and C, hypertension, dyslipidemia, obesity, obstructive sleep apnea, and depression. His surgical history included removal of an obstructing kidney stone 18 months earlier. His medications included inhaled fluticasone(Drug information on fluticasone)/salmeterol, inhaled levalbuterol, theophylline(Drug information on theophylline), montelukast(Drug information on montelukast), aspirin(Drug information on aspirin), atorvastatin(Drug information on atorvastatin), and atenolol(Drug information on atenolol). He had no known medication allergies. He denied tobacco use, excessive alcohol(Drug information on alcohol) use, and illicit drug use.
Pulmonary function testing revealed a forced expiratory volume in 1 second (FEV1) of 2.55 L (78% of predicted), forced vital capacity (FVC) of 3.59 L (82% of predicted), and FEV1:FVC ratio of 72%. Total lung capacity was mildly reduced at 4.87 L (75% of predicted), residual volume was reduced at 1.28 L (60% predicted), and slow vital capacity was reduced at 3.59 L (82% of predicted). His carbon monoxide–diffusing capacity was normal at 29.2 mL/min/mm Hg (108% of predicted). The flow-volume loop showed mild terminal coving of the expiratory limb, without evidence of inspiratory or expiratory blunting. The overall pattern was consistent with a mild restrictive ventilatory defect.
Pathological evaluation of the tissue obtained via forceps biopsy was consistent with bronchial schwannoma (Figure 3). Neither mitosis nor necrosis was identified, suggesting a benign tumor (Figure 4). On immunohistochemical staining, the neoplastic cells were positive for vimentin and S-100 protein and negative for human muscle actin and desmin, signifying that the tumor was of mesenchymal origin with neural differentiation (Figure 5). The cytobrush biopsy specimen did not reveal malignant cells.
Discussion
Endobronchial tumors can be either malignant or benign (Table 1).1-3 Neurogenic tumors are rare and can manifest at any age (with most occurring in young adulthood, after age 20 years).2 This type of tumor arises from peripheral nerves located within the bronchial wall, composed of nerve sheath Schwann cells, described as neurilemomas (schwannomas) or neurofibromas.4 Endobronchial schwannomas are extremely rare; the exact incidence is not known, although one institution reported that 0.2% of all lung tumors were primary neurogenic tumors.5,6
Schwannomas are encapsulated, single tumors attached to a nerve that originates from the peripheral nervous system. Neurofibromas are not encapsulated, are multiple in number, and occur within the nerve sheath.4 Benign features of schwannomas include an encapsulated mass, rare or no mitotic figures, and borderline pleomorphism well demarcated from surrounding tissue.5 Malignant features include an unencapsulated mass, perineural invasion, indistinct cellular borders, frequent mitotic figures, pleomorphic fusiform cells, areas of hemorrhagic and cystic degeneration, and metastasis.5,6,12 Histologically, schwannoma spindle cells are arranged in a highly cellular and palisading nuclei pattern (Antoni A) or a less cellular and more fibrous pattern (Antoni B).3,13
Biopsy specimens may be obtained during flexible bronchoscopy. If the neurogenic tumor is hypervascular, bronchoscopic biopsies should be performed in centers with experienced staff available to manage serious hemorrhagic complications.2 Interventional bronchoscopy and thoracic surgical expertise should be readily available. There are reports of surgical tumor resection without prior biopsy in patients with hypervascular tumors that are deemed too high a bleeding risk.4 Pathological evaluation of biopsy specimens should include immunohistochemical stains for vimentin and S-100 protein, to confirm neurogenic origin.
There is no uniform approach to the treatment of endobronchial schwannomas (Table 2). Historically, the standard treatment has been a surgical resection; however, given the benign nature of this tumor, less invasive options have evolved.15,16 Definitive treatment by tumor resection or laser therapy is recommended for symptomatic mass lesions not responsive to conservative management, such as bronchodilators and antibiotics, when indicated. However, the available therapeutic approaches are varied and must be carefully tailored to each specific clinical scenario.3,4,9,15,17 Watchful waiting is also an option for asymptomatic benign schwannomas in select patients.
The prognosis is generally good for benign lesions, as is expected in this case. Long-term follow-up may be needed given the slow growth of these tumors and the potential for recurrence after resection.2
