What are fetal lung masses?
Fetal lung masses form when a genetic or structural problem occurs during lung development. There are several types of lung masses and each reflects a different problem in lung development. Most importantly, the diagnosis needs to be confirmed. Often, fetal lung masses are misdiagnosed as the wrong type, or confused with other malformations, such as congenital diaphragmatic hernia.
The most common type of fetal lung mass is the congenital cystic adenomatoid malformation (CCAM). This occurs when part of the lung becomes blocked during development and does not develop properly. Click here for more information about CCAM.
The next most common fetal lung mass is a bronchopulmonary sequestration (BPS). This occurs when the airways do not connect to part of the lung, as if there was an error when the airway developed. The blood vessels also form abnormally. The BPS does not get blood flow like the rest of the lung. Rather, it steals blood flow away from the body via a separate artery. The lung mass itself can be within another part of the lung or separate, even in the abdomen. Click here for more information about BPS.
Another type of lung mass is a congenital lobar emphysema (CLE) lesion. This is actually a rare problem when an airway in the lungs becomes blocked or narrowed during fetal development. The airway malformation causes excessive growth of that part of the lung. This rarely causes a serious problem.
Even more rare is a fetal type of lung cancer called pulmonary blastoma. This lesion can look just like a CCAM. Unfortunately, the diagnosis can only be made after removing the mass.
How are fetal lung masses diagnosed?
Fetal lung masses can be seen in routine ultrasounds. Typically around 20 weeks of gestation, a routine ultrasound will show if the baby has a lung mass. The mass will appear as a bright area of the lung on ultrasound. MRI imaging can show us more about the nature and size of the mass, so we can help you and your family make the best possible decision about treatment.
What are the treatments and long term effects of lung masses?
The vast majority of fetal masses are benign (not cancerous), but they can cause a variety of problems for the fetus, even into childhood. Sometimes these problems must be managed before birth, sometimes at birth, but usually lung lesions can be managed after birth in a safe, elective setting. The major challenges facing a baby with a lung mass are:
- Heart failure:
Both CCAM and BPS lesions can grow rapidly before birth, straining the baby’s heart and causing heart failure. If it is not diagnosed and treated, the fetus can die. This usually occurs early in the second trimester. Treatment options will depend on the specific diagnosis, for more information click here to learn about BPS or CCAM.
- Pulmonary hypoplasia (small lungs):
If heart failure is not observed in the fetus, the lung mass can still be very large and prevent the development and normal function of the rest of the lung. If severe pulmonary hypoplasia is suspected, we may recommend a special delivery procedure, called an EXIT procedure. During this operation, the baby is delivered, but the placenta and umbilical cord remain attached, so we have time to see how the baby’s lungs function. If the lungs are very compromised, then the mass is removed just prior to birth to optimize expansion of the normal lung. Extracorporeal membrae oxygenation (ECMO) can also be used as a backup in case the lungs need more time to function optimally.
In lung masses that are connected to the normal lung, infection can occur after birth. Bacteria can pass from the normal lung into the lung mass. Because the lung mass has abnormal airways, the bacteria and mucous cannot be cleared and infection results. To prevent infection, we often recommend removal of the mass after birth to prevent infection.
- Lung cancer:
There are very few reports of fetuses having pulmonary blastoma, which is an extremely rare type of lung cancer. However, there are many reports of lung cancer developing within a CCAM in early adulthood. In CCAM, the abnormally developed lung tissue may already have a genetic predisposition to form cancer. With chronic infection and inflammation, lung cancer can form. This is why many parents elect to remove the CCAM after birth, essentially preventing any chance of lung cancer from the CCAM.
Overall, it is extremely rare for a baby to have problems before birth due to a lung mass. Most are benign, can be easily managed birth, and the resulting babies live happy, healthy lives. In the rare setting that intervention is required before birth, the St. Louis Fetal Care Center has the expertise to help your baby with the appropriate monitoring, treatment and intervention, whether that be via a needle or open fetal surgery.
Learn more about these conditions and treatment options: