Congenital cystic adenomatoid malformation

Congenital cystic adenomatoid malformation (CCAM) is a congenital disorder similar to bronchopulmonary sequestration. In CCAM, usually an entire lobe of lung is replaced by a non-working cystic piece of abnormal lung tissue. This abnormal tissue will never function as normal lung tissue.

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In most cases the outcome of a fetus with CCAM is very good. However in a rare few cases the cystic mass grows so large as to limit the growth of the surrounding lung and cause pressure against the heart. In these situations, the CCAM can be life-threatening for the fetus.

Diagnosis

CCAMs are often identified during routine prenatal ultrasonography. Indentifying characteristics on the sonogram include: an echogenic (bright) mass appearing in the chest of the fetus, displacement of the heart from its normal position, a flat or everted (pushed downward) diaphragm, or the absence of visible lung tissue.

CCAMS are classified into three different types based largely on their gross appearance. Type I has large (>2 cm) multiloculated cysts. Type II has smaller uniform cysts. Type III is not grossly cystic, referred to as the "adenomatoid" type. Microscopically, the lesions are not true cysts, but communicate with the surrounding parenchyma.

Treatment

In most cases, a fetus with CCAM is closely monitored during pregnancy and the CCAM is removed via surgery after birth. A few fetuses may develop fluid collections within the chest cavity and in those situations a Harrision catheter shunt can be used to drain the fluid into the amniotic fluid.

Very large cystic masses might pose dangerous during birth because of the airway compression. In this situation, a special surgical type of delivery called the EXIT procedure may be used.

In rare extreme cases, where fetus's heart is in danger, fetal surgery can be performed to remove the CCAM. If non-immune hydrops fetalis develop, there is a near universal mortality of the fetus. Fetal surgery can improve the survival percentage up to 50-60%.