Imaging description

Congenital cystic adenomatoid malformations (CCAMs) account for 25% of all congenital lung abnormalities. CCAMs are divided into three types: type 1 consists of cysts between 2 cm and 10 cm in diameter; type 2 consists of cysts between 0.5 cm and 2 cm in diameter; and type 3 consists of microscopic cysts [1–3]. Most lesions are identified within the first two years of life. However, in the rare cases where the lesions are not identified until adulthood, they are usually either type 1 or type 2 CCAMs. On imaging, type 1 CCAMs are most commonly a large cyst (up to 12 cm in diameter) or a few cysts, possibly containing air/fluid levels. Type 2 CCAMs are typically multicystic (2–20 mm in diameter) and may also contain air/fluid levels (Figure 14.1). CCAMs typically exhibit mass effect on the adjacent lung and when large enough can displace mediastinal structures. They are most commonly seen in the lower lobes and are surrounded by “normal” lung parenchyma.

Importance

CCAMs are a common congenital lesion of the lung and should be considered in the differential of pulmonary lesions detected in early childhood or prenatally. In the adult, the lesions are a cause of recurrent infection.