A congenital cystic adenomatoid malformation (CCAM) is a cystic piece of abnormal lung tissue that does not work like normal lung tissue. It usually replaces one part (lobe) of the lung. CCAMs occur with equal frequency in both lungs. We do not know what causes one part of the lung to develop abnormally, but we know that cystic tissue involved will never function as normal lung tissue.
There are several types of cystic lung disease including congenital cystic adenomatoid malformation (CCAM), pulmonary sequestration, and defects that are a mixture of these two. The abnormal piece of lung can be microcystic (many small cysts) or macrocystic (several large cysts). Pulmonary sequestrations are distinguished from CCAMs by a blood vessel that comes directly from the main artery (aorta). The type is not as important as the size and how much it enlarges during the pregnancy.
Congenital Cystic Adenomatoid Malformations vary in size at presentation and can change dramatically throughout the pregnancy. The diagnosis is made by prenatal ultrasonographic findings of an echogenic (bright) mass appearing in the chest of the fetus. Other ultrasound findings may include displacement of the heart from its normal position, a flat or everted (pushed downward) diaphragm, or the absence of visible lung tissue.
The majority of these fetuses have a very good outcome. The mass may grow with the fetus and appear quite large, but not cause trouble because the fetus is growing rapidly and there remains enough room for the normal part of the lung to grow. The mass may remain the same size, but because the fetus is growing rapidly, the abnormal piece of lung becomes relatively small. The mass may shrink in size or even disappear before birth. In all these cases, the outlook for a normal life is excellent.
For a minority of patients (less than 10%), the mass grows so large that it becomes life-threatening to the fetus. These fetuses develop hydrops—accummulation of fluid in the skin, chest, or abdomen that reflect severe heart failure. The mass can grow so large that it limits the growth of the lungs resulting in pulmonary hypoplasia, or small lungs. The mass can also push on the heart and the esophagus of the fetus, putting an extra workload on the heart and preventing the fetus from swallowing amniotic fluid. Often the first sign is a mother who measures too big for her due date because there is too much amniotic fluid.
Those who do not have hydrops when the lesion is first detected must be closely followed (link: becoming a patient) by doing ultrasounds at least every week to look for the development of hydrops. If they do not develop hydrops, we continue a ‘wait-and-see’ attitude with close follow-up. Many of these lesions will begin to decrease in size before 26 weeks of gestation and can be safely dealt with after birth at a tertiary perinatal center. Some lesions will even take care of themselves entirely.
Fetuses with very large rapidly growing lesions (usually between 20 and 26 weeks’ gestation) may develop hydrops (fetal heart failure) and become very ill with a severe risk of death. Fetuses with CCAM and hydrops will generally not survive unless something is done. In addition, severe hydrops can be a threat to the mother if the mirror syndrome develops, i.e., the mother “mirrors” the fetus’s illness, developing high blood pressure and fluid retention (edema).
In cases with extreme fetal hydrops, the mother may be at risk for maternal mirror syndrome, which is a condition where the mother's condition mimics that of the sick fetus. Because of a hyperdynamic cardiovascular state, the mother develops symptoms that are similar to pre-eclampsia and may include vomiting, hypertension, peripheral edema, proteinuria and pulmonary edema. Despite resection of the anomaly, maternal mirror syndrome may still occur.
In order to determine the severity of your fetus's condition it is important to gather information from a variety of tests and determine if there are any additional problems. These tests along with expert guidance are important for you to make the best decision about the proper treatment.
Amniocentesis may be necessary for chromosome testing. Sonography is the best imaging tool, but is dependent on the experience and expertise of the operator. Magnetic resonance imaging may be necessary in some cases. Many problems are first detected during routine screening procedures performed in your doctor's office (amniocentesis, maternal serum screening, routine sonography), but assessment of complex usually requires a tertiary perinatal/neonatal center with experience managing complex and rare fetal problems. We can work with your doctor to find a center convenient for you.