Ann Thorac Surg 2005;79:326-329
© 2005 The Society of Thoracic Surgeons
Case report
Cystic Adenomatoid Malformation of the Lung Presenting in Adulthood
Yolanda Herrero, MD*,a,
Inmaculada Pinilla, MD, PhDa,
Isabel Torres, MDa,
Manuel Nistal, MD, PhDb,
Mercedes Pardo, MDa,
Nieves Gómez, MD, PhDa
a Department of Radiology, Madrid, Spain
b Department of Pathology, Hospital Universitario La Paz, Madrid, Spain
Accepted for publication August 6, 2003.
* Address reprint requests to Dr Herrero, Hospital Universitario La Paz, Departamento de Radiodiagnóstico, Paseo La Castellana 261, Madrid 28046, Spain
yoliherrero{at}hotmail.com
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Abstract
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Cystic adenomatoid malformation is an uncommon embryonic developmental abnormality usually diagnosed in neonates and infants. Its presentation in adulthood is rare, with only 27 cases reported up to now. Due to its rarity, it is seldom suspected and adult physicians are not familiar with its clinical and radiologic features. We report two cases of cystic adenomatoid malformation presenting in adults, one as a recurrent pneumonia, and another as a coincidental finding on a chest roentgenogram. We describe the clinical features, radiologic and computed tomographic findings, and the histopathologic characteristics in this article, along with a review of the literature.
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Introduction
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Cystic adenomatoid malformation (CAM) is a rare abnormality of bronchopulmonary development involving the noncartilage-containing terminal structures that is characterized by disorganized overgrowth of respiratory bronchioles and intercommunicating cysts. Most cases are diagnosed antenatally or present in neonates and infants with severe respiratory distress or recurrent pulmonary infections in the affected lung. Occasionally CAM goes unrecognized until adolescence or adulthood. There are only 27 cases of late-onset CAM reported in the literature.
We report two cases of CAM presenting in adulthood, one as recurrent pulmonary infections, and the other as a chance finding on a chest roentgenogram. A review of the literature is made.
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Case Reports
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Patient 1
A 46-year-old woman was admitted to our hospital because of community-acquired left lower lobe pneumonia. Her medical history included a left lower lobe pneumonia episode 7 years earlier and a 10-pack-year history of smoking. No previous chest roentgenograms were available. The patient had fever and left pleuritic pain. On physical examination, a few crackles were heard over the lower third of the left lung without other findings. Laboratory tests showed leukocytosis with left shift and were otherwise unremarkable. Chest roentgenograms showed a nonhomogeneous opacity in the left lower lobe and an ipsilateral pleural effusion. These findings were interpreted as community-acquired pneumonia, and the patient was prescribed antibiotic treatment. Despite her clinical improvement, the lung consolidation did not resolve. Subsequently, a bronchoscopy and a chest computed tomographic scan were performed. The bronchoalveolar lavage was negative for malignancy. Blood and bronchoalveolar lavage cultures were negative for bacteria, mycobacterium, virus, and fungi. The chest computed tomographic (CT) scan was performed after the intravenous administration of contrast material, which disclosed an 8-cm mass with numerous cavities containing fluid (without enhancement) in the lower left lobe (Fig 1). Three months later a repeat CT scan showed disappearance of the fluid and multiple large air-filled cysts consistent with a CAM (Fig 2). A left lower lobectomy was performed without complications. Macroscopic examination revealed an 8 x 8 x 4.5 cm well defined but not encapsulated lesion that consisted of multiple cysts measuring up to 4 cm. Microscopically, the cysts were lined by pseudostratified ciliated columnar epithelium and scattered mucous cells, consistent with CAM type I (Fig 3).
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Fig 1. Patient 1: Enhanced computed tomographic scan shows mass with numerous cavities containing fluid in the lower left lobe.
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Fig 2. Patient 1: Three months later the computed tomographic image with wide window shows multiple fluid-filled cysts after fluid draining.
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Fig 3. Patient 1: Histologic section disclosed multiple cysts lined by pseudostratified ciliated columnar epithelium and scattered mucous cells consistent with CAM type I .
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The postoperative course of the patient was uneventful. Six months after surgery the patient was free from symptoms and the chest roentgenogram showed a well-expanded upper left lobe without lesions.
Patient 2
A 47-year-old man was admitted to our hospital because of a lung mass on a chest roentgenogram. The patient was asymptomatic. He had a 60-pack-year history of smoking. There was no history of chest pain, cough, hemoptysis, or dyspnea. Except for obesity, physical examination was unremarkable. Laboratory tests were normal. Chest roentgenogram showed an ill-defined right parahilar mass. The thoracic CT scan demonstrated a 4-cm soft-tissue mass in the lower right lobe (Fig 4). The lesion showed spiculated margins and a heterogeneous enhancement (after intravenous contrast administration) with central low attenuation areas. No lymph node enlargement or pleural effusions were detected. The bronchoscopy was normal, and transthoracic needle aspiration was nondiagnostic. A surgical resection of the mass was performed without complications. Macroscopic examination showed a 3-cm central cyst containing mucus surrounded by smaller ones with irregular margins. Histologically, the lesion was consistent with CAM type I.
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Fig 4. Patient 2: Enhanced computed tomographic scan shows a soft-tissue mass with spiculated margins and a heterogeneous enhancement with central low attenuation areas in the right lower lobe.
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The postoperative course was uneventful, and the patient has remained asymptomatic.
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Comment
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Cystic adenomatoid malformation is an uncommon, nonhereditary bronchopulmonary malformation of unknown cause, which results in an arrest in lung development at an early stage. Cystic adenomatoid malformation is usually unilateral, affecting either lung equally, and unilobar with no clear lobar predominance. Stocker and colleagues [1] classified CAM into three different histologic types, which are believed to be determined by the timing of the lung injury during embryologic life. The most frequent histologic classification is type I, which accounts for 50% to 70% of cases and is characterized by a single large cyst or by multiple large cysts (at least 2 cm in diameter) with a pseudostratified ciliated columnar epithelium resembling the distal bronchial tree and proximal acinus with normal alveoli between the cysts. This may be the result of an injury during the pseudoglandular or canalicular period of lung development. Type II represents 20% to 40% of cases and consists of multiple terminal bronchiolar-like small cysts (< 1 cm in diameter) that resemble the canalicular period. Type III represents as many as 10% of cases and is characterized by a solid mass composed of structures mimicking terminal bronchioles and alveolar ducts, resembling the pseudoglandular period. Neoplastic transformation, including bronchioalveolar [2] carcinoma and a case of rhabdomyosarcoma [3] has been reported in older children and young adults with CAM.
We believe that 27 cases of late-onset CAM have been reported [4–8]. In the vast majority of cases reported (88%), as in our 2 patients, the pathologic findings were consistent with Stocker's type I. Whereas other visceral malformations have been reported in as many as 18% of children with CAM, mainly renal and cardiac anomalies in type II, there is only one case (3.7%) of adult-onset CAM associated with cavernous transformation of the portal and splenic veins and osseus vertebral malformation [7]. The most common clinical presentation of late-onset adult CAM is the recurrent pulmonary infections limited to the abnormal lobe or a lung abscess (40.7%) as in our patient 1 case report, due to the difficulty to drain the secretions formed in the cysts that subsequently become infected. Other clinical forms of presentation include pneumothorax (14.8%), hemoptysis (14.8%), dyspnea (3.7%), or coincidental discovery in chest roentgenograms (18.5%).
Chest roentgenogram findings are nonspecific and depend on the extension of the lesion and its clinical presentation. Consolidations have been described that were indistinguishable from a lobar pneumonia or an intrapulmonary water density mass with well defined margins that may contain lucent cystic areas or an air-fluid level resembling a lung abscess or pneumatocele [5, 6]. Small CAM lesions may not be visible on chest roentgenograms [6].
Computed tomography is the technique of choice for assessment of CAM lesions. On CT scan, type I CAM is characterized by large cysts (> 1 cm in diameter) that may be air-filled, fluid-filled, or that contain air-fluid levels. Areas of enhancement after intravenous contrast injection or areas of low attenuation around the cysts, corresponding to smaller cysts lesions and normal parenchyma can also be seen [6]. In patient 1 (previously described) who presented with recurrent lung infections, the initial CT findings included a large lesion with multiple cystic areas containing fluid in relation to retained fluid secretions with appearances that changed over time as the fluid drained to lucent cysts. In contrast, patient 2 (previously described) who was asymptomatic at diagnosis, presented as a spiculated lung mass with heterogeneous enhancement resembling a neoplasm. These two patients highlight the wide radiologic expression of CAM and the difficulty in making a correct preoperative diagnosis. Radiologic differential diagnosis must be made with pulmonary sequestration, bronchiogenic cyst, cystic bronchiectasis, diaphragmatic hernia, and infected tumors [6, 8].
Histologic examination was identical in our two patients. The lesions were comprised of multiple cysts lined by pseudostratified ciliated columnar epithelium and scattered mucous cells. In some cysts the epithelium was strikingly hyperplastic and contained numerous mucous cells. Pulmonary parenchyma around the cysts and surrounding the lesions were normal. Histologic differential diagnosis of CAM includes pulmonary sequestration, bronchiogenic cyst, and simple foregut cyst.
Unlike other cyst malformations, surgical resection of CAM lesions is advocated (even for asymptomatic patients) to prevent infection and because of its potential neoplastic transformation [4, 6, 8].
In summary, CAM is a rare congenital malformation of the lower respiratory tract that may be diagnosed during adulthood. It must be included in the differential diagnoses of any individual with recurrent lung infections or pneumothorax or with unresolving lung infiltration. These findings should prompt further assessments using CT scans to facilitate the diagnosis. In view of the malignant potential, surgical management is recommended.
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References
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- Stocker JT, Madwell JE, Drake RM. Congenital cystic adenomatoid malformation of the lung. Hum Pathol. 1997;8:156–171
- Granata C, Gambini C, Balducci T, et al. Bronchioloalveolar carcinoma arising in a congenital cystic adenomatoid malformation in a child: a case report and a review of the malignancies originating in CCAM. Pediatr Pulmonol. 1998;25:62–66[Medline]
- D'Agostino S, Bonoldi E, Dante S, et al. Embryonal rhabdomyosarcoma of the lung arising in cystic adenomatoid malformation: case report and review of the literature. J Pediatric Surg. 1997;32:1381–1383[Medline]
- Hellmuth J, Glerant JC, Sevestre H, et al. Pulmonary adenomatoid malformation presenting as unilobar cysts in an adult. Respir Med. 1998;92:1364–1372[Medline]
- Dahabreh J, Zisis CH, Vassiliou M, et al. Congenital cystic adenomatoid malformation in an adult presenting as lung abscess. Eur J Cardiothorac Surg. 2000;18:720–723[Abstract/Free Full Text]
- Lujan M, Bosque M, Mirapeix RM, et al. Late-onset congenital cystic adenomatoid malformation of the lung. Respiration. 2002;69:148–154[Medline]
- Lackener RP, Thompson AB, Rikkers LF, et al. Cystic adenomatoid malformation involving an entire lung in a 22-year-old woman. Ann Thorac Surg. 1996;61:1827–1829[Abstract/Free Full Text]
- Zach MS, Eber E. Adult outcome of congenital lower respiratory tract malformations. Thorax. 2001;56:65–72[Free Full Text]
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Abstract
Introduction
