University of California San Francisco

Congenital Pulmonary Airways Malformation

What is a congenital pulmonary airways malformation of the lung?

The normal lung is made up of five individual lobes - three lobes form the right lung and two lobes form the left lung. When one of these lobes forms incorrectly in a developing fetus, it is called a Congenital pulmonary airways malformation (CPAM) or also known as congenital cystic adenomatoid malformation (CCAM). Congenital pulmonary airways malformation is a fluid-filled, or cystic, mass of abnormal lung tissue that doesn't work like normal lung tissue. You may hear it described as a tumor, but it is not cancerous. It is simply a growth of abnormal cells in a lobe of your baby's lung. Although it is not known why these form, the condition usually isn't associated with other birth defects or with abnormal chromosomes.

Prenatal diagnosis and fetal treatment

Prenatal ultrasound may show a bright or echogenic mass in the baby's chest. The size of the mass varies with each fetus. Other ultrasound findings may show that the mass has caused the heart to move from its normal position and that it has flattened the diaphragm, which should be bow-shaped. Normal lung tissue may be difficult to see on the ultrasound if it is "hidden" or behind the mass.

Your obstetrician may request frequent ultrasounds to measure the size of the mass. The time interval between ultrasound studies depends on your individual case. When a fetus has a CPAM, usually one of two things may happen.

  • The mass in the lung may actually start to shrink and seem to "disappear." This is because the mass has stopped growing while the baby's chest continues to develop.
  • Conversely, the mass may continue to grow during your pregnancy. At the end of your pregnancy, your obstetrician - in consultation with neonatologists (doctors who specialize in treating newborns) and pediatric surgeons - will advise you on a delivery plan.

For more information about prenatal diagnosis and fetal treatment visit Fetal Treatment Center: CPAM

What will happen after my baby is born?

Some babies have difficulty breathing after birth and may require extra oxygen or an immediate operation to remove the mass. If this happens, your baby may stay in the hospital for one to two weeks. Other infants have no symptoms at birth and go home with their parents two or three days after birth. For these babies, we recommend a special X-ray called a CT scan performed at 3 months of age. You will need to contact the pediatric surgical office at (415) 476-2538 to schedule this procedure. After the CT scan, the pediatric surgeons will meet with you to discuss whether your baby will need an operation to remove the CPAM mass. The timing of the operation varies with each patient, but usually is performed in the first few years of life.