Congenital Cystic Adenomatoid Malformation (CCAM)
Congenital cystic adenomatoid malformation (CCAM) is a congenital lung lesion. CCAMs are classified into three types based upon their pathologic characteristics, according to specialists at the University Center for Fetal Medicine. Type I lesions are the most common and consist of large cysts that are few in number. Type II lesions consist of smaller, more numerous cysts. Congenital anomalies are frequently reported with Type II lesions, and the outcome is dependant upon the associated anomalies. Type III lesions are the least common and consist of larger masses that have very small cysts or microcysts.
CCAMs can be seen on a routine prenatal ultrasound. A patient is then referred to a tertiary care center for additional testing to rule out other anomalies and to follow the growth of this mass.
The prenatal evaluation should include a high-resolution ultrasound, including doppler evaluation to exclude a systemic blood vessel supplying the mass, in order to distinguish a type III CCAM from a bronchopulmonary sequestration (BPS). A fetal MRI will help define the anatomy, aid in the correct diagnosis and rule out other structural anomalies. In addition, fetal echocardiogram should be performed to rule out cardiac anomalies and evaluate cardiac function.
A MRI (right) shows a fetus with a right upper lobe CCAM indicated by the arrow. The large cyst is consistent with a Type 1 CCAM. No systemic feeding vessel was identified on ultrasound.
The growth of these masses is variable between 22 and 28 weeks gestation. Once detected, the lesions should be followed closely until a growth rate has been determined or growth has reached a plateau after 28 weeks. If there is mass effect on the mediastinum or a large dominant cyst which increases the risk for air-trapping, delivery should occur at a tertiary care center where a pediatric surgeon, neonatal intensive care unit (NICU) and extracorporeal membrane oxygenation (ECMO) are available.
Treatment of CCAM varies by case. Fetal intervention may be needed if the fetus develops hydrops. Treatment of the fetus depends upon gestational age and the type of CCAM. Fetuses developing hydrops at 30 weeks or later may be considered for early delivery and resection of the mass at birth using a specialized delivery called the EXIT procedure. Fetuses with CCAMs who develop hydrops prior to 30 weeks may be candidates for fetal surgery to resect the mass. If there is a large dominant cyst, the placement of a thoracoamniotic shunt to relieve the pressure can be performed. Additionally, the use of corticosteroids to promote lung maturity and halt the growth of lesions in utero has been reported, but not verified by clinical trials.
Treatment of the newborn with CCAM also varies by the type of lesion. The baby should be examined thoroughly for respiratory distress. If no symptoms are present, the newborn may be able to undergo surgical resection at a later time (approximately one month of age). Newborns who exhibit symptoms will require resection of the mass. Recovery time and length of hospital stay depend on the condition of the baby.