CCAM (Congenital Cystic Adenomatoid Malformation) is a condition in which part of the lungs develop benign growths that become cystic. The cysts can range from being large to very small. They put pressure on the heart and the regular lung tissue within the pleural space, and as such, can cause a range of problems occurring both during the fetal stage and after birth.

Problems occurring as a result of CCAM are highly dependent on the size of CCAM. Small CCAMs cause hardly any problems during the fetal stage, but large CCAMs can put pressure on regular lung tissue, causing hypoplasia of the lung, or put pressure on the heart, resulting in fetal hydrops (of which main observations are ascites, pleural effusion, pericardial fluid retention and subcutaneous edema). If pressure is placed on the esophagus, it can prevent the fetus from swallowing, resulting in polyhydramnios, which can cause premature delivery or premature rupture of membranes.

The size (volume) of CCAM is measured by ultrasound examination and calculated using the following formula.

CCAM volume (cm³) = Tumor major axis (cm) x minor axis (cm) x height (cm) x 0.52

An index used in measuring the size of CCAM without reference to the number of weeks’ gestation and the size of the fetus is the CCAM Volume Ratio (CVR). CVR uses the following formula for calculation:

CVR = CCAM volume (cm³) / head circumference (cm)

Since past reports show that a CVR of 1.6 or more yields a high probability of the occurrence of fetal hydrops, such cases require particularly careful observation.

Since small CCAMs cause almost no problems during the fetal stage or at birth, they do not particularly require treatment and can be managed by observation alone. For cases in which the CCAM is large, it will very likely be necessary to provide respiratory support immediately after birth and in some cases, emergency surgery may also be required. For this reason, it is recommended that delivery take place at a tertiary medical care center, where a pediatric surgeon can provide an emergency response when necessary.

Since it is believed that there is a high risk of fetal or neonatal death in cases where fetal hydrops has been noted, premature delivery or fetal therapy are required. In CCAM cases with large cysts, the positioning of a cyst-amniotic cavity shunt should be considered, while in CCAM cases with small cysts, the administration of adrenal cortex hormones (steroids) to the mother should be considered.