Cystic Adenomatoid Malformation Workup

Updated: Dec 08, 2015
  • Author: Anne E Stone, MD; Chief Editor: Michael R Bye, MD  more...
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Workup

Laboratory Studies

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  • Laboratory studies are generally not helpful in the diagnosis of congenital cystic adenomatoid malformation (CCAM).
  • Perform routine karyotyping on all amniotic fluid obtained from the child after birth; however, incidence of chromosomal anomalies associated with CCAM is extremely low.
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Imaging Studies

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  • Chest radiography is essential in the workup of the child with suspected CCAM. [23, 24] See image below.
    The CT scan of the chest reveals a right lower lob The CT scan of the chest reveals a right lower lobe congenital cystic adenomatoid malformation (CCAM) in a 6-week-old infant who presented with tachypnea. The most striking feature is the solitary enlarged cyst surrounded by numerous microcysts. This lesion was resected without complication.
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    • Chest radiography almost invariably identifies CCAM of sufficient size to cause clinical problems.
    • The usual appearance is of a mass containing air-filled cysts.
    • Other radiological signs that may be evident include mediastinal shift, pleural and pericardial effusions, and pneumothoraces. The diagnosis may not be clear from chest radiography alone. Chest radiography may reveal a mass without any evidence of cysts.
    • In cases in which the cystic lesion involutes, chest radiography may not allow sufficient definition to determine whether the CCAM has completely disappeared.
  • CT scanning [25]
    • CT scanning of the thorax provides a safe and rapid means of defining the extent of CCAM in all age groups.
    • The typical appearance is of multilocular cystic lesions with thin walls surrounded by normal lung parenchyma. The presence of superimposed infection with the lesion may complicate the appearance.
    • Air fluid levels may be evident.
    • CT scanning of the chest may outline additional coexisting lesions. Series have suggested a small percentage of cases thought to have resolved antenatally that demonstrated persistence of lesions on CT scan.
    • The definition of high-resolution chest tomography (HRCT) is sufficient to differentiate between microcystic and macrocystic lesions.
  • Prenatal ultrasonography [3, 26]
    • With increasing use and technical ability of prenatal ultrasonography and sonographers, most cases of congenital lung anomalies are prenatally diagnosed. No specific diagnostic features of CCAM allow the ability to distinguish it unequivocally from other lung lesions such as congenital lobar emphysema or pulmonary sequestration.
    • Ultrasonography may demonstrate evidence of hydrops, such as fetal ascites or pleural effusions.
    • Type I lesions (see Histologic Findings) appear as multiple large cystic areas in the lung. In type II lesions, multiple small cysts are evident on ultrasonography. Because of the extremely small size of the cysts in type III lesions, the prenatal ultrasonographic appearance is often one of a homogenous mass.
  • MRI [27, 28]
    • MRI permits increased definition of a particular lesion, thereby enhancing the clinician's ability to accurately diagnose and offer an informed prognosis.
    • Additionally, maternal problems that prevent the optimal use of fetal ultrasonography, such as obesity, poor fetal lie, and oligohydramnios, pose no obstacle to MRI. MRI may be useful particularly in distinguishing CCAM from congenital diaphragmatic hernia.
    • Lastly, no maternal or fetal exposure to ionizing radiation occurs in contrast to the use of CT scanning.
  • Other imaging studies
    • Perform renal and cerebral ultrasonography in all newborns with CCAM in order to exclude coexisting renal and CNS anomalies.
    • Perform echocardiography in all newborns with CCAM to rule out any coexisting cardiac lesions. Furthermore, in infants with respiratory distress, echocardiography may provide evidence of persistent pulmonary hypertension (eg, right-to-left shunting, increased pulmonary artery pressures).
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Procedures

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  • Amniocentesis may be indicated to obtain amniotic fluid for karyotyping.
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Histologic Findings

CCAM has been described as a hamartoma, namely, abnormal tissue with an excess of one or more tissue components. CCAMs generally communicate with the bronchial tree and derive their blood supply from the pulmonary circulation, in contrast to pulmonary sequestration, which derives its blood supply from the aorta. [4]

In 1977, Stocker grossly classified CCAM into 3 types based mostly on cyst size, as follows:

  • Type I includes multiple large cysts (>2 cm in diameter) or a single large cyst surrounded by numerous smaller cysts. Type I is the most common type of CCAM and is associated with an excellent prognosis. [12]
  • Type II CCAM has multiple small cysts, usually less than 1 cm in diameter, and accounts for over 40% of cases of CCAM. In Stocker's series, as many as 60% of type II lesions are associated with other congenital anomalies that may affect prognosis, specifically renal agenesis. [12]
  • Type III CCAMs are large and account for less than 5% of all cases. They consist of multiple microcysts, measuring less than 0.5 cm in diameter. [12]

In 1993, Adzick reported his group system of classification. Microcystic lesions (cysts measuring < 5 mm) were usually associated with fetal hydrops and, hence, a poor prognosis. Macrocystic lesions (ie, cysts >5 mm) were not usually associated with hydrops and had a good prognosis. [3]

More recent classification divides lesions into 5 types (0-5) of pulmonary airway malformations based on the site of the tracheobronchial/acinar structures where malformation developed. Type 0 refers to acinar atresia (a tracheobronchial defect) and type 4 has multiple cysts lined by flattened epithelium (an alveolar defect). [2, 29]

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Other Tests

A study by Barikbin et al reported that postnatal lung function tests can detect and monitor congenital cystic adenomatoid malformation and that these tests represent an additional tool to support the decision for or against surgical intervention. [30]

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