Quiz Answer

Congenital cystic adenomatoid malformation (CCAM)—Our patient's chest radiograph shows a large cystic area in the left chest with mediastinal shift to the right, suggestive of CCAM or congenital lobar emphysema. In contrast, the computed tomography (CT) scan of his chest shows a septated, multicystic lesion, which is characteristic of CCAM.

Pulmonary sequestration, bronchogenic cysts, CCAM, and congenital lobar emphysema represent congenital bronchopulmonary malformations.¹ Presumably, abnormal lung development during weeks 5 to 8 of gestation produces the proliferation of dysplastic interconnected bronchoalveolar structures, resulting in cysts of variable sizes surrounded by a rim of cuboidal or columnar epithelium.²

CCAM is rarely associated with additional anomalies, appears to be more common in males, and tends to be unilateral. These lesions were first described in 1949 by Ch'in and Tang.³ In 1977, Stocker and Drake further classified CCAM into three subtypes based on the size, shape, arrangement, and histology of the cystic elements.⁴ Type 1 CCAM is the most common subtype and consists of multiple cysts that measure 2 cm or larger in diameter; it also tends to have the best prognosis. Our patient had a type 1 CCAM and did well after undergoing a left lower lobectomy. Type 2 lesions typically consist of smaller and more uniform cysts, whereas type 3 lesions have a bulkier glandular appearance and tend to be more extensive, involving an entire lobe or lung.

Infants often present in respiratory distress; however, symptoms and chest radiographic findings are variable and depend on the extent of lung involvement. There are also rare reports of delayed presentations in adults, who most commonly present with recurrent pulmonary infections.⁵ Advances in ultrasonography have increased antenatal diagnosis of CCAM. CT scanning offers greater detail and diagnostic sensitivity, but histopathologic analysis is required to make a definitive diagnosis.⁶

Complete lobectomy is curative if segmental resection is not possible. Although interventions in asymptomatic antenatal patients are more controversial, resection is still generally recommended because of an increased risk of infection and the rare potential for malignant transformation.⁷

Infants with diaphragmatic hernias can also present with difficulty breathing; however, plain radiographs will often show loops of fluid- or air-filled bowel in the chest along with an abnormal bowel gas pattern. Intrapulmonary sequestration tends to be diagnosed during childhood and adolescence and appears as a well-circumscribed, uniform mass in the posterior segments of the left lower lobe on chest radiography.¹ In congenital lobar emphysema, the chest radiograph may look similar to CCAM, but CT scanning often shows attenuated vessels to the affected lobe and demonstrates the nonmulticystic nature of this lesion.^8,9

References

1. Shanmugam G, MacArthur K, Pollock JC. Congenital lung malformations—antenatal and postnatal evaluation and management. Eur J Cardiothorac Surg. 2005;27:45-52.
2. Fulghum HW, Vasquez EP. Congenital cystic adenomatoid malformation: a case study. The Internet Journal of Advanced Nursing Practice. 2003;5(2). Available at: www.ispub.com. Accessed February 16, 2008.
3. Ch'in Y, Tang M. Congenital adenomatoid malformation of one lobe of a lung with general anasarca. Arch Pathol Lab Med. 1949; 48:221-229.
4. Stocker JT, Drake RM. Congenital cystic adenomatoid malformation of the lung. Classification and morphologic spectrum. Hum Pathol. 1977;8:155-171.
5. Takeda S, Miyoshi S, Inoue M, et al. Clinical spectrum of congenital cystic disease of the lung in children. Eur J Cardiothorac Surg. 1999;15:11-17.
6. Winters WD, Effmann EL. Congenital masses of the lung: prenatal and postnatal imaging evaluation. J Thorac Imaging. 2001;16:196-206.
7. Khosa JK, Leong SL, Borzi PA. Congenital cystic adenomatoid malformation of the lung: indications and timing of surgery. Pediatr Surg Int. 2004;20:505-508.
8. Wiersma HE, Veenhoven RH, Sprikkelman AB, et al. Pitfalls in the diagnosis of congenital lobar emphysema. Ped Clin Amsterdam. 2001;12. Available at: www.crstaalm.dds.nl. Accessed February 17, 2008.
9. Karapurkar SA, Borkar JD, Birmole BJ. Malformation of lung in neonates (lobectomy for congenital lobar emphysema and lung cyst). J Postgrad Med. 1993;39:224-227.