CCAM stands for congenital cystic adenomatoid malformation, a rare lung condition where an abnormal mass of tissue develops in a baby’s lung before birth. The condition affects roughly 1 in 10,000 births. Today, most doctors use the updated name CPAM (congenital pulmonary airway malformation), but CCAM remains widely used, and they refer to the same thing. The name was changed to better reflect the variety of tissue types involved, since not all forms are cystic and not all contain the adenomatoid tissue the original name implied.
How CCAM Develops
During pregnancy, a baby’s lungs develop through five overlapping stages that begin around the fourth week of gestation and continue into early childhood. CCAM forms when something disrupts the normal branching and growth of the airways during one of these stages. The signaling between different cell layers that guides lung development goes awry, leading to an overgrowth of abnormal tissue that forms cysts or solid masses in one section of the lung.
The specific stage of development where the disruption occurs determines what type of CCAM a baby has and how the tissue looks. Disruptions earlier in development tend to affect the larger airways, while later disruptions involve the smallest air sacs at the tips of the lungs. No specific gene or environmental exposure has been identified as a consistent cause.
The Five Types
CCAM is classified into five types (Type 0 through Type IV) based on where in the airway the abnormal tissue originates and how large the cysts are.
- Type 0 originates from the largest airways (the windpipe and main bronchi). It accounts for only 1% to 3% of cases and is almost always fatal.
- Type I is the most common form and carries the best prognosis. It features one or more cysts larger than 3 centimeters in diameter.
- Type II makes up about 15% to 30% of cases. The cysts are smaller (under 2 centimeters) and mixed with solid areas of tissue.
- Type III is uncommon, accounting for 5% to 10% of cases. The cysts are so tiny the mass appears mostly solid on imaging, and these lesions tend to be large.
- Type IV occurs in the most distal part of the lung and contains multiple large cysts similar to Type I. It accounts for 5% to 15% of cases.
Type I and Type IV together make up the majority of diagnoses, and both generally have favorable outcomes with treatment.
How CCAM Is Found
Most cases are discovered during a routine prenatal ultrasound, typically between 18 and 24 weeks of pregnancy. The mass shows up as a bright (echogenic) area within the baby’s chest. Some lesions contain visible fluid-filled cysts, while others appear more solid depending on the type.
Once detected, doctors track the size of the mass relative to the baby’s head circumference using a measurement called the CCAM Volume Ratio, or CVR. This ratio is calculated by estimating the volume of the mass (using its three dimensions) and dividing by the head circumference. A CVR above 1.6 signals a higher risk of hydrops, a dangerous condition where fluid builds up in the baby’s body. Pregnancies with a CVR above that threshold are typically monitored two to three times per week.
Some CCAM lesions shrink significantly or even become undetectable on ultrasound as the pregnancy progresses. However, “disappearing” on ultrasound does not mean the tissue is gone. A CT scan after birth usually confirms that abnormal lung tissue remains.
What Happens During Pregnancy
Most pregnancies with a CCAM diagnosis proceed without major complications. The baby is monitored with regular ultrasounds to track the size of the mass and watch for signs of hydrops.
When hydrops does develop, steroid injections given to the mother can help shrink the lung mass. Studies show that after a single course of steroids, hydrops resolves in about 70% of cases, with an overall survival rate around 84%. In cases treated with two or more courses, improvement occurs in roughly 47%, with survival around 82%. For the most severe cases that don’t respond to steroids, fetal surgery to drain large cysts or reduce the mass may be considered, though this is rare.
After Birth: Symptoms and Timing
Some babies with CCAM have breathing difficulty immediately after birth if the mass is large enough to compress the surrounding healthy lung. These newborns need prompt evaluation and often early surgery.
Many babies, however, are born with no symptoms at all. In these cases, the question becomes when to operate. This is one of the more debated topics in pediatric surgery. Most pediatric surgeons worldwide (about 62%, based on an international survey) perform elective surgery between 6 and 12 months of age. The reasoning is that symptoms like recurrent lung infections tend to develop around 5 to 10 months, and removing the mass during infancy takes advantage of a window when the remaining lung can still grow to compensate. Some centers prefer earlier surgery, at 1 to 6 months, to reduce infection risk and maximize compensatory lung growth.
Research comparing different surgical timings has found no difference in complication rates or mortality, which suggests that neonates can undergo surgery as safely as older infants.
What Surgery Looks Like
The standard treatment is surgical removal of the affected lung lobe (lobectomy) or, in select cases, removal of just the affected segment (segmentectomy). Today, more than half of these operations are performed thoracoscopically, using small incisions and a camera rather than a large chest incision.
In a study of over 2,100 infants, the thoracoscopic approach was associated with a shorter hospital stay. The median stay was 3 days for both approaches, but the distribution favored thoracoscopic surgery. After adjusting for differences between patient groups, complication rates, readmission rates, and mortality were similar between the two techniques. Overall complication rates (including readmissions) were about 13% to 14% regardless of approach, and mortality was very low at under 1%.
Long-Term Lung Function
One of the most reassuring aspects of CCAM treatment is how well children recover after surgery. When a lobe of the lung is removed during infancy, the remaining lung tissue grows to fill much of the space. Studies tracking children for up to 11 years after lobectomy have found that total lung volume reaches approximately 90% of what would be expected for their age and size, even when 8% to 45% of the lung tissue was removed.
That said, this compensatory growth is mostly about volume rather than fully functional new tissue. Some children show subtle findings on detailed testing, such as mildly elevated residual air volume or small areas with decreased blood flow. In practical terms, though, most children live active lives without noticeable limitations. Studies comparing lobectomy to the more conservative segmentectomy have found no significant difference in lung function at medium-term follow-up, which means the extent of the surgery doesn’t appear to change the outcome meaningfully.
The Question of Cancer Risk
One reason surgeons often recommend removing CCAM tissue even in babies with no symptoms is a small but real association with a rare childhood lung cancer called pleuropulmonary blastoma (PPB). In its earliest form, PPB is made up entirely of cysts and can look identical to CCAM on imaging. In a registry of 350 confirmed PPB cases, about 10% of early-stage cystic tumors progressed to more aggressive forms within a median of about two years. Because there’s no reliable way to distinguish a harmless CCAM from an early PPB on imaging alone, surgical removal allows the tissue to be examined under a microscope and eliminates that uncertainty. This cancer link is one of the strongest arguments against a “wait and watch” approach for asymptomatic lesions.