What is the name of the abnormality that involves multicystic formation on the lung, specifically Congenital (CPAM) in a fetus or newborn?

Congenital Pulmonary Airway Malformation (CPAM)

The abnormality involving multicystic formation in the lung is called Congenital Pulmonary Airway Malformation (CPAM), formerly known as Congenital Cystic Adenomatoid Malformation (CCAM). 1, 2

Definition and Classification

CPAM is a developmental malformation of the lung characterized by cystic lesions that replace normal lung tissue. 3, 4 The condition is classified into distinct types based on cyst size and histological features:

• Type I (Macrocystic): Large cysts greater than 2 cm in diameter, lined by columnar pseudostratified epithelium 4, 5
• Type II: Multiple smaller cysts less than 1-2 cm in diameter with more uniform size, lined by flattened cuboidal epithelium 4, 6, 5
• Type III (Microcystic): Solid-appearing masses containing microscopic cysts that resemble the pseudoglandular stage of lung development 4, 5

Clinical Presentation

CPAM is the most frequent congenital lung malformation and can present across a spectrum from asymptomatic prenatal findings to life-threatening respiratory distress. 3, 4

Prenatal Manifestations

• Space-occupying lesions cause mediastinal shift, impairing venous return and cardiac output 1
• Esophageal compression results in polyhydramnios 1
• Large lesions can lead to nonimmune hydrops fetalis, which is associated with poor prognosis 7, 2

Postnatal Manifestations

• Respiratory distress at birth requiring immediate surgical intervention 1, 3
• Recurrent pneumonia 3
• Spontaneous pneumothorax (rare but serious complication) 3, 6
• Some cases remain asymptomatic 4

Diagnostic Approach

Prenatal ultrasound is the primary screening tool, appearing as cystic and/or hyperechoic fetal lung lesions detected during the second trimester. 4 The American College of Obstetricians and Gynecologists recommends:

• Serial ultrasound monitoring throughout pregnancy to detect complications and plan delivery 1, 4
• Echocardiography to evaluate for associated cardiac anomalies and hemodynamic effects 1
• Fetal MRI can provide additional prognostic information in select cases 3

Management Strategy

Fetal Intervention (for complicated cases with hydrops)

All CPAM cases with hydrops must be referred to a tertiary center with expertise in fetal therapy. 2

For macrocystic CPAM with hydrops:

• Perform thoracoamniotic shunt placement or needle drainage of large cysts causing mediastinal shift, which improves survival to greater than 50% 2
• If gestational age is near term (≥34 weeks), consider needle drainage immediately before delivery rather than shunt placement 2

For microcystic CPAM with hydrops:

• Administer maternal betamethasone or dexamethasone as first-line treatment 1, 2, 3
• This has become standard of care over the last decade and has reduced the need for fetal surgical procedures 3

Monitoring for Complications

• Monitor for polyhydramnios and mirror syndrome, which indicate worsening fetal cardiovascular compromise 2
• Serial maternal blood pressure monitoring is essential due to risk of mirror syndrome 2
• Development of mirror syndrome generally indicates delivery if gestational age permits 2

Delivery Planning

Even non-hydropic cases should deliver at centers with pediatric surgery and neonatal intensive care capabilities. 2

• For stable non-hydropic cases, allow spontaneous labor at term 2
• If hydrops develops after 32-34 weeks, consider delivery rather than fetal intervention depending on lung maturity 2
• Hydrops developing before 32 weeks may be amenable to fetal intervention 2

Postnatal Management

Large lung malformations causing early postnatal respiratory distress require immediate surgical intervention. 1, 3

• The treatment of choice is surgical resection by segmentectomy or lobectomy 8
• Many children are candidates for minimally invasive thoracoscopic approaches as an alternative to thoracotomy 3
• Elective resection is typically performed after birth for lesions that do not regress 7

Important Caveats

Consider CPAM in the differential diagnosis of any neonate presenting with respiratory distress and mediastinal shift on chest radiograph. 8 This is critical for respiratory therapists, nurses, and neonatal transport teams. 8

Even asymptomatic lesions warrant consideration for surgical resection due to reported association with malignancy in unresected CPAM. 3, 8, 4

Prognosis

In the vast majority of cases, the overall prognosis remains excellent. 3 The prognosis is favorable in the absence of pulmonary hypoplasia, fetal hydrops, or associated congenital anomalies. 5