Acquired unilateral bronchomegaly secondary to pulmonary carcinoid tumour

Dear Editor, Bronchomegaly refers to abnormal dilation of the bronchi in the absence of inflammation or structural damage, distinguishing it from bronchiectasis.[1] It is typically diagnosed when the bronchial diameter exceeds three standard deviations above the mean of the population.[1] The condition is rare, and its prevalence remains poorly defined due to the limited number of symptomatic cases. Bronchomegaly is most commonly described in the context of Mounier-Kuhn Syndrome (MKS), a congenital disorder affecting the trachea and upper bronchi, usually presenting bilaterally.[2] It is a rare entity with an estimated prevalence of 0.5–1% as detected on bronchoscopy.[2] We report a rare case of acquired unilateral bronchomegaly secondary to a pulmonary carcinoid tumour. CASE A 25-year-old woman presented with a two-year history of haemoptysis and exertional dyspnoea. She denied systemic symptoms such as fever, weight loss or anorexia. Chest radiography revealed partial collapse of the right lower lobe. Computed tomography (CT) showed an endobronchial mass lesion in the right main bronchus [Figure 1]. A Ga-68 DOTANOC PET/CT scan demonstrated radiotracer uptake in the lesion. Flexible bronchoscopy revealed a well-circumscribed endobronchial mass extending into the lower trachea. Endobronchial debulking and cryoablation were performed. Histopathology confirmed a typical carcinoid tumour (low-grade pulmonary neuroendocrine neoplasm). Post-debulking, the right main bronchus appeared dilated in the region of the bulky carcinoid mass lesion. Further, excessive dynamic airway collapse (EDAC) was absent.Figure 1: Right main bronchus focal bronchomegaly. Top panel: Radiology at presentation. (a) Chest radiograph. The right lung shows volume loss with extensive bronchiectasis. The trachea is shifted to the right. There is an intraluminal growth (arrow) projecting from the right main bronchus into the lower trachea. (b and c) Computed tomography of the chest showing the intrabronchial growth (arrow) along with extensive right lung bronchiectasis and volume loss. Bottom panel: Radiology after debulking of the intrabronchial growth. (d) Chest radiograph. The right lung shows signs of aeration. Lung volume loss has decreased. The right main bronchus is widened in comparison to the left main bronchus (arrow). (e and f) Computed tomography of the chest showing improvement in aeration. The arrows show the marked difference in the diameters of the right and left main bronchiAfter the debulking procedure, the individual became asymptomatic. Surveillance bronchoscopy one-month post-procedure showed no pooled secretions and revealed persistent enlargement of the right main. The left bronchial tree appeared normal. A second bronchoscopy six months later confirmed persistent unilateral bronchomegaly [Figure 2]. Retrospective review of imaging showed consistent findings pre- and post-procedure. A follow-up Ga-68 DOTANOC PET/CT scan showed no residual tracer-avid lesions.Figure 2: Bronchoscopic examination in unilateral bronchomegaly. (a) Pre-debulking view of the growth as seen in the right main bronchus. (b) Immediate post debulking. The carina (black arrowhead) and the dilated right main bronchus (white arrow) are visible. (c) Follow-up at 1 month. The carina (black arrowhead) and the dilated right main bronchus (white arrow) are visible. (d) Surveillance at 6 months. The right main bronchus (white arrow) shows an abnormal diametric widening (yellow lines) compared to the left main bronchus (black arrow)Bronchomegaly is an uncommon finding, particularly when unilateral. It may result from chronic intraluminal pressure exerted by a slow-growing mass, such as a carcinoid tumour. This pressure, known as circumferential hoop stress, is well described in the context of cylindrical airways and can lead to plastic expansion and cartilage atrophy, resulting in airway dilation.[3,4] While tracheomegaly is more commonly associated with mechanical causes such as prolonged intubation, carcinoid tumours exhibit slow growth, with a median volume doubling time of 2.7–4 years.[5,6] The precise relationship between tumour growth rate and expansile pressure remains unclear. Unlike MKS, which typically presents with bilateral airway dilation and EDAC, this case demonstrated unilateral bronchomegaly without EDAC. The absence of expiratory collapse and pooled secretions suggests a distinct pathophysiology. Management included airway clearance techniques and ongoing surveillance to monitor for recurrence and assess reversibility of bronchial dilation. This case illustrates a rare presentation of acquired unilateral bronchomegaly secondary to a pulmonary carcinoid tumour. Recognition of atypical causes and differentiation from congenital syndromes such as Mounier-Kuhn are essential for appropriate management. Surveillance bronchoscopy remains a valuable tool in monitoring airway changes and guiding long-term care. Learning points Unilateral bronchomegaly may result from chronic intraluminal pressure due to slow-growing tumours. Differentiation from MKS is critical due to differing clinical implications and management. Surveillance bronchoscopy is essential for monitoring airway changes and assessing reversibility. Consent: Patient anonymity has been maintained in the manuscript. This manuscript and images were submitted after informed consent by the patient. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.