British Journal of Radiology (2003) 76, 339-342
© 2003 British Institute of Radiology
doi: 10.1259/bjr/29778480
Mucoepidermoid carcinoma in a patient with congenital agenesis of the left upper lobe
H Pandya, MBChB, MRCS and
S Matthews, MRCP, FRCR
Department of Radiology, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK
Correspondence: Dr S Matthews
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Abstract
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This report describes an unusual case of a mucoepidermoid carcinoma developing in a patient with congenital left upper lobe agenesis. Mucoepidermoid tumours most often develop in major bronchi and present as lobar collapse, post-obstructive pneumonia or as a mass lesion on chest radiography. On CT, the tumour is smooth, well defined, homogeneous and may enhance with intravenous contrast. Tumour calcification has been reported. Lobar agenesis often presents as a co-incidental finding on chest radiography as total or almost complete absence of aeration of the affected lung. Thoracic CT confirms the presence of the underdeveloped lung, pulmonary artery and bronchus and associated mediastinal shift and herniation of the contralateral lung. A literature review of these two conditions is presented.
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Introduction
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Pulmonary agenesis is an extremely rare congenital anomaly with an estimated incidence of between 0.0034% and 0.0097% [1]. It has been reported to be associated with many congenital anomalies related to the cardiovascular, spinal, renal and musculoskeletal systems, but has not been reported in association with tumour formation [2, 3]. Mucoepidermoid carcinoma of the tracheobronchial tree is a slow-growing neoplasm comprising 0.1–0.2% of primary lung malignancies. The aetiology of this tumour is not known. There have been no previous reports of bronchial mucoepidermoid carcinoma in a patient with unilateral lobar agenesis. The literature regarding these two rare conditions has been reviewed and the radiology described.
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Case report
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A 23-year-old man presented with recurrent episodes of haemoptysis, cough and occasional purulent sputum. He had immigrated to the United Kingdom from Pakistan a year prior to presentation. He was a non-smoker who had previously been fit and well. Examination was normal except for the presence of bronchial breathing in the left lower lobe. Spirometry showed a reduced forced expiratory volume (FEV1) of 68% predicted. Sputum culture and microscopy did not demonstrate acid-fast bacilli. A chest radiograph demonstrated marked loss of volume in the left hemithorax with ill-defined opacification in the left lower zone (Figure 1
). On thoracic CT there was a completely collapsed, small left lung with a rudimentary left bronchial tree and small left pulmonary artery (Figure 2). Air-filled cavities and an area of calcification were seen within the collapsed left lung. At bronchoscopic bronchography using 10 ml iotrolan 300 (Isovist 300, Schering, Berlin, Germany), a polypoid tumour was found close to the origin of the left main bronchus, bronchiectasis was noted within the left lower lobe and the upper lobe bronchus was absent (Figure 3). The patient subsequently underwent a left pneumonectomy and made an uneventful recovery.
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Figure 1. Posteroanterior chest radiograph showing reduced volume in the left hemithorax with collapse of the left lower lobe.
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Figure 2. Helical CT of the thorax: (a) Lung windows demonstrating marked left mediastinal shift and hyperinflation of the right upper lobe into the left upper hemithorax. Cavitation is seen in the collapsed left lower lobe. Mediastinal windows displaying (b) the small left pulmonary artery (long arrow) and (c) calcification in the left lower lobe (short arrow), possibly within the tumour.
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Figure 3. Bronchographic bronchography with iotrolan 300 showing bronchiectasis of the posterior basal segment of left lower lobe (arrow heads) and non-filling of the remaining segmental bronchi due to endobronchial tumour (arrow). There was no evidence of upper lobe bronchi.
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Macroscopic examination of the lung specimen showed a rounded beige and brown bronchial tumour occluding the left lower lobe bronchus with widespread bronchiectatic change distally within the lower lobe. There was evidence of sepsis with mucopurulent and haemorrhagic secretion accumulation. A rind of dense fibrous tissue replaced the upper lobe tissues. No upper lobe bronchi were identified. Microscopically, the tumour contained mucus containing, squamous, clear and eosinophilic polygonal cells with minimal pleomorphism. The appearances favoured a neoplastic process of salivary phenotype in keeping with a mucoepidermoid tumour. A diagnosis of a Grade II mucoepidermoid carcinoma in a patient with unilateral agenesis of the left upper lobe was made.
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Discussion
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Mucoepidermoid carcinoma of the tracheobronchial tree is a rare neoplasm [4]. Patients vary in age from 3 months to 78 years, but nearly half are younger than 30 years. In adults the symptoms are mainly related to airway obstruction and include pneumonia, persistent cough and less frequently haemoptysis [5]. The lack of specificity of these symptoms and rarity of the tumour accounts for the delay in correct diagnosis. Histologically, the tumour is characterized by a mixture of mucus-secreting cells, squamous cells and cells of intermediate type. Epidermoid areas are made up of cells without marked pleomorphism, with a large amount of cytoplasm and normal nuclei. High grade malignancy is rare in both adult and paediatric cases [6]. The term "bronchial adenoma" has been used to collectively describe mucoepidermoid carcinoma and other slow-growing neoplasms including, adenoid cystic carcinoma, carcinoid tumours and mixed tumours [7]. Since these tumours are low grade malignancies, the term "bronchial adenoma" is a misnomer and should be discarded.
Mucoepidermoid carcinomas are usually located in segmental bronchi and less commonly arise within the trachea, main bronchus or lobar bronchus, as in this case, and very rarely within the supraglottic region [8]. They are usually easily visualized at bronchoscopy. The tumour is macroscopically polypoid and is frequently covered with relatively normal respiratory epithelium. As a result, bronchial lavage and brushing have a low diagnostic yield. An iceberg-like appearance of these tumours has been described [9]. Bronchial mucoepidermoid carcinomas can appear as a solitary pulmonary nodule or mass with or without associated post-obstructive pneumonia or atelectasis, an endobronchial nodule or as a mass with a distal cavitary lesion on posteroanterior chest radiographs [10]. The incidence of presentation as a solitary pulmonary nodule on chest radiograph is variable and has been reported in 71% and 42% of cases in two series [4, 10]. On CT imaging the tumours are central, smoothly oval or lobulated, homogeneous, may contain calcification and may show mild contrast enhancement [4]. Hilar or mediastinal lymphadenopathy is not frequently observed. In our case, the endobronchial tumour could not be clearly defined on the CT scan but areas of calcification were noted adjacent to the left lower lobe bronchus, possibly within the tumour.
Pulmonary agenesis is an extremely rare congenital malformation that may take a number of forms. Spencer characterized pulmonary agenesis into (1) bilateral complete agenesis (2) unilateral agenesis with (a) complete absence of bronchi, (b) rudimentary bronchus, or (c) poorly developed main bronchus with poorly organized parenchyma, and (3) lobar agenesis [11]. 70% of cases were left sided and there was a male predominance in one series [12]. The aetiology of pulmonary agenesis remains obscure. A limited number of cases of unilateral pulmonary agenesis have been reported within families suggesting possible autosomal recessive inheritance [1, 13, 14]. Developmentally, the tracheo-bronchial groove appears in the fourth week of fetal life as a median ventral diverticulum of the foregut from which lung buds develop. The lung buds are supplied by a pair of branchial arteries that form in the second month of development [15]. Interruption of arterial development is postulated to result in necrosis of an established lung bud or smaller distal airway with subsequent pulmonary or lobar agenesis [16]. In mice, fibroblast growth factor 10 (Fgf10) has been reported to be an important regulator of limb and lung formation without which the mice die at birth owing to lack of lung development [17].
The findings on the chest radiograph in cases of agenesis are characterized principally by total or almost complete absence of aeration in the affected lung, ipsilateral mediastinal shift and herniation of the normal lung into the upper zone of the affected hemithorax [18]. In lobar agenesis the volume of the affected lung is reduced and fat may take up the space normally occupied by a fully developed lung [19]. CT of the thorax demonstrates marked mediastinal shift and herniation of the contralateral lung [20, 21]. In addition, CT is able to demonstrate the degree of underdevelopment of the ipsilateral pulmonary artery and bronchus. Therefore, CT is useful in differentiating agenesis (complete absence of tissue), aplasia (presence of bronchus without pulmonary tissue) and hypoplasia (presence of a bronchus with rudimentary pulmonary tissue). In our case, the left upper lobe bronchus and pulmonary artery were absent and the left main pulmonary artery hypoplastic. Therefore, CT confirmed left upper lobar agenesis. Also, CT can be used to non-invasively distinguish conditions that may mimic lung agenesis radiographically: total atelectasis from any cause, bronchiectasis with collapse and advanced fibrothorax [18, 21].
Finally, bronchoscopic bronchography is performed infrequently and at few centres [22, 23]. The technique involves direct placement of the bronchoscope into the airways to be examined. The isosmolar non-ionic dimer iotrolan is injected via the operating channel into the bronchi and rapid sequence imaging at 2 frames per second are taken. In this case, it was able to clearly define bronchial anatomy and demonstrate the obstructing lesion of the left lower lobe causing non-filling of the remaining segments with contrast medium, bronchiectasis of the posterior segment and an absence of filling of the left upper lobe bronchus.
This case highlights the utility of combining multiple imaging modalities to adequately confirm bronchial anomalies. In addition, the development of the rare mucoepidermoid carcinoma in a patient with lobar agenesis has not previously been reported.
Received for publication July 10, 2002.
Revision received September 17, 2002.
Accepted for publication October 21, 2002.
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Abstract
Introduction
