2005 - TMH: Lady with “difficult” asthma
Dr. Thomas J.S. Lee; Department of Medicine, Tuen Mun Hospital
Our subject is a 28 years old Indonesian Chinese lady who presented to our hospital in April 2004 with shortness of breath associated with palpitations, coughs, sputum and fever.
She had been in Hong Kong for 6 years, and had enjoyed good past health with no history or family history of atopy. She had 2 prior pregnancies before, which were complicated by pregnancy-induced hypertension, requiring induction of labour at term, and both resulted in normal vaginal delivery. She does not smoke or drink any alcohol, but her husband does smoke regularly.
On physical examination, she was noted to be dyspnoeic, her temperature was 38.1°C, heart rate was 150/min, and there was generalized wheeze in her chest with right basal crepitations heard. Her other systems were otherwise normal. Her CXR showed right lower zone infiltrates. Her blood investigations results showed: WCC 29.4 x 109/L (92% polymorphs, eosinophil count was not raised), Hb 13.6 g/dl, Plt 237, ABG: pH 7.44, pCO2 4.52 kPa, pO2 11.07 kPa, SaO2 97%, liver & renal function was normal.
She was treated as suffering from chest infection and suspected asthma with antibiotics and bronchodilators. Her symptoms improved and fever subsided so she was discharged planned for a pulmonary function test.
She defaulted follow-up but was readmitted again in October and November 2004 with similar symptoms. She was treated with bronchodilators and steroids and her symptoms seemed to improve. A pulmonary function test showed a severe obstructive ventilatory limitation with insignificant bronchodilator response.
Her lateral CXR showed a distal tracheal opacity.
CT thorax performed which showed a intra-luminal polypoid soft tissue mass at the distal trachea with near total luminal occlusion.
She underwent emergency rigid bronchoscopy and the mass was debulked. She had an uneventful post-operative course.
Histology of the mass showed a tumour with many tubular epithelial elements in sheets that was intermixed with a myxochondroid stroma. At the edges the epithelial cells seemed to stream into the stroma. There were also islands of squamous cell metaplasia. All these were consistent with the diagnosis of a pleomorphic adenoma of the trachea.
Primary tracheal tumours are rare in clinical practice and usually either squamous cell carcinoma, or adenoid cystic carcinoma. Tracheal pleomorphic adenoma is extremely rare. Only 28 cases have been reported in the literature to date with the patient’s age ranging from 15 to 80 years old. It is more common in male patients, occurring more in the upper third followed by middle and lower third of the trachea. 2 malignant cases have been reported, 1 from Japan, and 1 from Turkey. It is very similar to that found in the salivary glands and its pathogenesis is controversial. It may originate from the epithelial glands of the submucosal glands, but peripheral lesions in the lungs have also been reported, so it may have arise from primitive stem cells.
Patients usually present with episodic coughs, dyspnoea on exertion, wheezing, haemoptysis, stridor, hoarseness, recurrent respiratory tract infections, and even dysphagia.
Macroscopically, these tumours varies in size, they are sessile, of a whitish grey colour on the surface, firm and polypoid in shape. The cut surface is firm, gray in colour and may be slightly mucoid.
Microscopically, they are seen to arise from the subepithelial tissues and are covered by respiratory and squamous epithelium. The glands are tubular and exhibits a varying amount of eosinophilic material. These epithelial elements are mixed with a myxochrondroid stroma which is rich in alcian blue-staininig mucopolysaccharide. There are foci of squamous metaplasia and the tumour cells are positive to S-100 protein, cytokeratin, glial fibrillary acidic protein, muscle specific actin, and vimentin.
Tumours that are small, and well circumscribed tend to be benign, while those that are larger, more infiltrative or poorly circumscribed tend to recur but rarely metastasize. The main differential diagnosis is adenoid cystic carcinoma which is a more aggressive tumour, with amorphous periodic acid schiff positive tubular material with absence of cartilagenous foci, perineural invasion, and has growing features.
The treatment of choice is complete excision with cuffs of normal tissue to avoid recurrence. This would usually involve removing a section of the trachea followed by reanastomosis.
References
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