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Congenital Cystic Adenomatoid Malformation (CCAM)

CCAM is a hamartoma of the lung that may involve a whole lung or a single lobe. Multiple cysts replace pulmonary parenchyma. It can also occur in lung sequestration. The cysts are usually unilateral and are classified into three types as follows:

     Fig 1

  • macrocystic (type I): few in number and large, up to 7 cm, and thick-walled
  • mixed (type II): multiple and smaller (about 1 cm)
  • microcystic (type III): very small, <0.5 cm, and not visible as distinct cysts by ultrasound; the lesions appear as bulky, intrathoracic, solid masses with increased echogenicity.

Incidence: Unknown.

Sonographic findings:

Fig 2, Fig 3, Fig 4

  • Echogenic or sonolucent mass in one side of the chest possibly shifting the heart.
  • Unilateral in most cases.
  • Hydrops fetalis (<10% of cases), commonly seen with a large mass, in particular a greater CAM volume ratio.
  • Polyhydramnios (65% of cases) secondary to esophageal obstruction from the intrathoracic mass, obstructed venous return or decreased absorption of lung fluid.
  • Doppler study reveals a normal blood supply, unlike the sequestration.
  • Main differential diagnosis:
    • If cystic mass: CCAM, CDH, bronchogenic or neuroenteric cyst, esophageal duplication
    • If solid mass: microcystic CCAM, pulmonary sequestration, CHD.
  •  Pitfalls:
    • Most often confused with congenital diaphragmatic hernia.
    • Acoustic enhancement posterior to the heart mimicking microcystic mass.
    • The normal thymus may occasionally simulate hypoechogenic mass.
  • First diagnosable between 12 and 18 weeks of gestation

Fig 1:  Schematic drawing: The three type of CCAM: type I (large cysts of variable size), type II (small cystic type), and type III (solid appearance)

Fig 2:  Cystic adenomatoid malformation   Oblique sagittal scan of the fetal trunk: solid-cystic mass (*), mostly cystic, in the left chest (CCAM type I)

Fig 3:  Cystic adenomatoid malformation   Oblique sagittal scan of the fetal trunk: echogenic mass in the left chest (solid circle)

Fig 4:  Cystic adenomatoid malformation  Oblique sagittal scan of the fetal trunk: partial solid and partial cystic mass in the left chest (CCAM type II)

Video clips of congenital cystic Adenomatoid malformation (CCAM)

CCAM (Congenital cystic adenomatoid malformation; CCAM)  Coronal scan of the chest: large echogenic mass (solid circle) in the left thorax with some cystic changes

CCAM (Congenital cystic adenomatoid malformation: CCAM)   CCAM type III: Large echogenic lung mass with mediastinal shift

Laryngeal Atresia :  Bilateral enlarged echogenic lung caused by high airway obstruction, associated with ascites, simulating bilateral CCAM type III

Associations: Usually not associated with other anomalies.

Prognosis: Good prognosis in the majority of cases especially the cystic type and it can spontaneously regress antenatally, but can not continue after birth; poor prognosis if associated with hydrops, especially microcystic type, lung hypoplasia, prematurity or severe associated malformations.

Management: Follow-up ultrasound examination is required, with no active intervention in the absence of acute polyhydramnios or hydrops. Persistent CCAM needs postnatal surgical removal.

Recurrence risk: Unknown.