INTRODUCTION: Primary tracheal adenoid cystic carcinoma (ACC) is a relatively rare salivary gland-type neoplasm originating in the bronchial gland. The tumor can go undiagnosed for months to years because of its nonspecific presenting symptoms, slow-growth, and silent nature. We describe a case of respiratory failure secondary to ACC presenting with near complete obstruction of bilateral main stem bronchi misdiagnosed as severe asthma exacerbation.
CASE PRESENTATION: 51-year-old Korean female was admitted for severe asthma exacerbation. She was diagnosed with asthma 2 years prior. No prior history of tobacco use. Upon admission, her temperature was 100.4 F, blood pressure was 135/60 mmHg, heart rate was 120 beats/min, respirations were 32 breaths/min, and pulse oximetry was 94% on room air. She was moderately uncomfortable using accessory muscles for breathing. Lung auscultation revealed diffuse wheezes. Laboratory examination including complete blood count and comprehensive panel were unremarkable. Arterial blood gas revealed pH 7.49, PCO2 34, PO2 157, HCO3 26 on 2 liters by nasal canula. A chest X-ray showed hyper-expansion of the lungs. Spirometry showed a severe obstructive ventilatory defect. The patient became increasingly tachypneic, short of breath, and developed respiratory failure requiring endotracheal intubation and mechanical ventilation within 24 hours of admission. Despite maximal medical treatment for asthma and appropriate ventilator management, her condition continued to decline. She developed worsening hypercarbia, elevated peak pressures of 80 cm H2O, and bilateral pneumothoraces. Bilateral chest tubes were placed. A CT scan reviewed in addition to pneumothoraces, small polypoid intraluminal mass with narrowing at the level of the carina and bilateral main stem bronchi. Bronchoscopy reviewed white-yellow lobulated intraluminal masses obstructing the tracheal lumen at the level of the carina, extending into the left and right main stem bronchi with resultant marked narrowing of both bronchi. Biopsies of the mass disclosed adenoid cystic carcinoma. The patient was transferred to another facility and underwent laser resection, stent placement of the trachea, bilateral main stem bronchi, and successful extubation. She subsequently received radiation therapy.
DISCUSSIONS: Primary adenoid cystic carcinoma of the lung accounts for about 0.2% of primary lung cancers. It is considered a low-grade malignancy due to its slow growth and relatively long clinical course, with a tendency for local recurrence and late metastasis. Symptoms are nonspecific and stem from chronic bronchial obstruction or irritation, averaging 2 years in duration prior to diagnosis. Patients with ACC of the trachea are significantly younger at presentation compared to those with squamous cell carcinoma (SCC) with an average age of 44 years. Unlike SCC, adenoid cystic carcinoma is more common in non-smokers. There seems to be a predilection for women. Presenting symptoms include dyspnea, chronic cough, hoarseness, stridor/wheezing, hemoptysis, and difficulty clearing secretions. Symptoms are often misdiagnosed as asthma, or in smokers, as chronic obstructive pulmonary disease (COPD). Even with detailed history and physical exam, visualization of the airways is essential in diagnosis. CT scan and/or bronchoscopy should be considered in those who fail optimal presumed obstructive airway disease treatment. Surgical resection is the preferred and first-line treatment, followed by postoperative radiotherapy. Complete tumor resection is essential since recurrence is high when there is residual tumor. In one study, the 5-year survival rate is 91% in the resected group and 40% in the non-resected group. ACC is not responsive to chemotherapy.
CONCLUSION: Tracheal adenoid cystic carcinoma can easily be misdiagnosed due to its nonspecific presentation and slow clinical course. When a patient presents with nonspecific respiratory symptoms including dyspnea, cough, wheezing, a tracheal primary tumor should be in the differential diagnosis, particularly in whom optimal treatment for presumed asthma or COPD fails.
DISCLOSURE: Michelle Cao, None.