Teaching Case

A 66-year-old woman presented with sudden-onset shortness of breath and wheeze, triggered by smoke and cold on a background of recurrent pneumonia. Auscultation demonstrated expiratory wheeze and decreased air entry throughout. She was treated for Chronic Obstructive Pulmonary Disease. On consultant review, stridor was noted, leading to further imaging.

On presentation, an initial CXR (Fig. 1) showed a hyper-inflation of the chest and a flattening of the hemi-diaphragms. A tracheal stenosis at the clavicular level was overlooked.
Chest CT with contrast (Fig. 2) showed a reduction of the tracheal lumen, below the thyroid, extending 3.5 cm inferiorly, with compression of the oesophagus.
Urgent bronchoscopy showed a 90% narrowing, and biopsies revealed a moderately differentiated squamous cell carcinoma. The tumour was debulked by diathermy excision, and a tracheostomy was inserted, fitting a T-tube to stent the trachea and maintain luminal patency.
Follow-up CT (Fig. 3) was performed to re-stage the growth, demonstrating residual tumour left of - and left posterior to the T-tube (measuring 13 mm in depth). The bronchial walls appear thickened throughout, and two new tree-in-bud opacities are noted in the right upper lobe.
Further bronchoscopy and CXR (Fig. 4) confirmed the T-tube to be in a satisfactory position.

A. Background
The trachea is a rare origin for tumours, accounting for fewer than one percent of respiratory tumours [1]. The incidence of primary tracheal malignancy is 0.1 per 100, 000 population per year, and the 10-year survival rate is 6-7% [2]. More than half of these tumours are squamous cell carcinomas (54.5%) [3].

B. Clinical Perspective
Progressive dyspnoea, cough, and phlegm are symptoms present in both chronic obstructive pulmonary disease and in tracheal malignancies which may mask the manifestation of the latter [4, 5]. The presence of stridor is a distinctive feature of an upper airway obstruction. Stridor is a harsh sound of a vibrating nature due to turbulent airflow, and can be inspiratory, expiratory, or biphasic. The different types are most commonly due to obstruction above the glottis, obstruction at/below the lower trachea, or a result of a glottic/subglottic lesion, respectively [6].

C. Imaging Perspective
Radiologically, tracheal cancers can be broadly divided in the following: intra-luminal, wall-thickening, and exophytic [3]. Due to the largely hyper-inflated chest on the initial CXR, it was easy to attribute the presenting symptoms of dyspnoea to the patient’s COPD, and overlook the tracheal stenosis that disguised under the sternal shadow. In addition, the patient was partially rotated, further complicating identification. Fortunately, a CT chest uncovered the underlying pathology, leading to prompt diathermic resection. Bronchoscopy further enabled the team to assess the severity, phenotype, and histology of the tumour, confirming the cause and degree of stenosis.

D. Outcome
The patient was treated palliatively due to comorbidities and the severity of her symptoms. She was profoundly cachexic and received adjuvant radiotherapy with 27 Gy (six fractions, twice per week - over five weeks). Although intended to be palliative, follow up CTs and biannual chest radiographs show no signs of recurrence up to this date, eight years after initial presentation. Of note, her follow-up CXRs are less hyper-inflated, though we did not have lung function tests available for comparison.

E. Teaching points
This case reminds us of the importance of review areas when interpreting CXR. Presenting symptoms may be due to the contributory effects of multiple pathologies, and to consider this on presentation is crucial, especially in complex patients with a number of comorbidities. This case also reminds us of the diagnostic benefit of stridor--clinical examination ultimately prompted further imaging.