Congenital pulmonary airway malformation (CPAM, formerly CCAM — congenital cystic adenomatoid malformation) is a hamartomatous cystic or solid lung mass originating from terminal bronchioles during lung development. Classified by Stocker into five types (Type 0-4); Type 1 (large cysts, >2 cm) and Type 2 (small cysts, <2 cm) are most common. CPAM usually involves a single lobe and has normal bronchial connection and pulmonary arterial supply (unlike sequestration). Detected on prenatal US as a cystic or solid thoracic mass. Postnatal CXR shows cystic air spaces (bubble appearance) or solid opacity. CT is the gold standard for determining cyst size, location, and Stocker type. Surgical resection (lobectomy) is recommended even in asymptomatic cases — due to malignant transformation risk (bronchioloalveolar carcinoma in type 1, pleuropulmonary blastoma in type 4) and recurrent infection risk.
Age Range
0-1
Peak Age
-
Gender
Equal
Prevalence
Rare
CPAM originates from abnormal proliferation of terminal bronchioles during the pseudoglandular phase (weeks 5-17) of embryological lung development. Instead of normal airway branching, excessive terminal bronchiole proliferation and absence of mature alveolar tissue creates a hamartomatous mass. Cystic spaces form from expansion of abnormal bronchiolar structures — lined with ciliated epithelium and connected to airways, filling with air (hence radiolucent cystic areas on CXR). The cystic appearance on CT reflects these dilated bronchiolar structures. The solid component (especially Type 3) results from primitive alveolar tissue proliferation. CPAM is supplied by normal pulmonary artery — no systemic arterial supply (key difference from sequestration). Has connection with normal bronchial tree — therefore cysts can become infected and fill with air. Malignant transformation risk exists in type 1 (mucinous cells with bronchioloalveolar carcinoma potential) and type 4 (pleuropulmonary blastoma).
The signature finding of CPAM is a cystic or mixed lung mass containing variable-sized cysts in a single lung lobe on CT. CT angiography confirms pulmonary arterial supply (no systemic arterial supply — not sequestration). These two findings together (cystic mass + pulmonary arterial supply) confirm CPAM diagnosis and Stocker typing is based on cyst size.
CT is the gold standard for CPAM diagnosis and classification. Type 1: one or few large cysts (>2 cm, dominant cyst may be >10 cm) — air or fluid-filled, thin-walled. Type 2: multiple small cysts (<2 cm) — homogeneous microcystic pattern. Type 3: solid mass (cysts microscopic, appears solid on CT). Type 4: large peripheral cysts — associated with pleuropulmonary blastoma. Usually single lobe involvement. Compression of surrounding lung and mediastinal shift may be seen. In first postnatal days, cysts may be fluid-filled (opaque) — become radiolucent as air replaces fluid.
Report Sentence
A lung mass containing multiple cystic structures is seen in the ___ lobe of the ___ lung, with the largest cyst measuring ___ cm; findings are consistent with CPAM Type ___.
CXR may show various appearances of CPAM. Type 1: single or few large radiolucent cystic areas — may have air-fluid levels. Type 2: multiple small radiolucencies ('Swiss cheese' appearance). Type 3: solid homogeneous opacity — consolidation or mass-like. Immediately after birth cysts may be fluid-filled and appear opaque — within hours-days air fills creating radiolucent cystic appearance. CXR is sufficient for initial assessment but CT is needed for Stocker typing and surgical planning.
Report Sentence
On CXR, multiple cystic radiolucencies/solid opacity are seen in the ___ lobe of the ___ lung; consistent with CPAM diagnosis.
On prenatal US, CPAM appears as a cystic (macrocystic — large anechoic areas, Type 1) or solid echogenic mass (microcystic/solid — Type 2/3) in the thorax. Macrocystic CPAM is easily recognized — large anechoic cystic areas. Microcystic/solid type appears as homogeneous echogenic mass and requires differential from pulmonary sequestration. Cardiac deviation, polyhydramnios, and fetal hydrops are poor prognostic findings. Some CPAMs may spontaneously regress prenatally.
Report Sentence
On prenatal US, an echogenic/cystic mass is seen in the ___ hemithorax with contralateral cardiac displacement; consistent with CPAM.
CT angiography confirms that CPAM is supplied by the pulmonary artery — this feature is critical in differentiating from sequestration. In sequestration, abnormal feeding artery from the aorta or other systemic arteries is seen, while in CPAM all vascular supply is from normal pulmonary artery. Venous drainage is also via normal pulmonary veins. Hybrid lesions (CPAM + sequestration) are possible — both cystic/solid CPAM component and systemic arterial supply coexist. CT angiography is essential for surgical planning.
Report Sentence
On CT angiography, the lesion is supplied by pulmonary artery branches with no systemic arterial supply; this vascular pattern is consistent with CPAM.
Large CPAM lesions cause mass effect pushing mediastinal structures contralaterally and compressing ipsilateral other lobes. Mediastinal shift appears on CXR and CT as cardiac and tracheal deviation. Contralateral lung may be partially atelectatic from pressure effect. In neonates, large CPAM can cause respiratory distress. Prenatally, massive CPAM can cause fetal hydrops — compression of great vessels impairs venous return.
Report Sentence
Mass effect of the CPAM lesion has displaced mediastinal structures contralaterally.
Criteria
One or few large cysts (>2 cm, dominant cyst usually 3-10 cm). Most common type (60-70%).
Distinct Features
Good prognosis. May contain mucinous cells — bronchioloalveolar carcinoma transformation risk. Surgical resection recommended.
Criteria
Numerous small cysts (<2 cm, usually 0.5-2 cm). 15-20% of cases.
Distinct Features
Associated anomalies frequent (60%) — renal agenesis, cardiac anomalies, diaphragmatic hernia. Prognosis depends on associated anomalies.
Criteria
Solid mass — cysts microscopic, appears solid on CT. 5-10% of cases. May involve entire lobe or entire lung.
Distinct Features
Poor prognosis — massive mass effect and pulmonary hypoplasia. Fetal hydrops frequent. Mediastinal shift prominent.
Criteria
Large peripheral cysts, thin walls, alveolar tissue origin. Strong association with pleuropulmonary blastoma (PPB).
Distinct Features
DICER1 mutation should be investigated. PPB is a malignant tumor — if solid component develops in cystic lesions followed as CPAM, urgent resection is needed.
Distinguishing Feature
Sequestration shows systemic arterial supply (from aorta) — CPAM is supplied by pulmonary artery. CT angiography confirms this distinction. Hybrid lesions are possible.
Distinguishing Feature
In CDH, diaphragmatic defect is present with abdominal organs in thorax. In CPAM, diaphragm is intact and lesion is pulmonary origin.
Distinguishing Feature
In CLE, hyperinflated lobe is seen — no cystic structures, uniform hyperinflation. In CPAM, discrete cystic structures are seen.
Urgency
routineManagement
surgicalBiopsy
Not NeededFollow-up
specialist-referralCPAM is treated with surgical resection (lobectomy) — recommended even in asymptomatic cases due to malignant transformation risk (bronchioloalveolar carcinoma in type 1, pleuropulmonary blastoma in type 4) and recurrent infection risk. Symptomatic neonates may require emergency surgery. Asymptomatic cases typically undergo elective surgery at 3-6 months. Prognosis is excellent in type 1 and 2 (>95% survival after surgery). Type 4/PPB may require malignancy treatment.
Most commonly detected congenital lung anomaly in the prenatal period. Large lesions can cause hydrops fetalis and pulmonary hypoplasia. CVR (CPAM volume ratio) >1.6 increases hydrops risk. Spontaneous regression is possible but complete disappearance is rare (may be hidden on imaging). Risk of malignant transformation (pleuropulmonary blastoma, 1-4% in Type 1) makes elective resection controversial but generally recommended. Recurrent pneumonias in symptomatic cases indicate surgery.