The expanded classification of CPAM includes the original types 1, 2, and 3, and two new types: 0 and 4.
- Type 0: Represents an abnormality of the trachea and mainstem bronchi. Incompatible with life.
- Type 1: Represents an abnormality of the bronchial/proximal bronchiolar region. The most common type (60%). Single or multiple large cysts (2–10 cm in diameter) surrounded by smaller cysts and a compressed normal parenchyma. CT shows one or more large, air-filled cysts with or without gas-fluid levels. MR shows T2-hyperintense uni- or multilocular lesions with discrete walls.
- Type 2: Represents an abnormality of the bronchiolar region. Small cysts (0.5 cm - 2 cm). Second most common type (20%). Frequently associated with other congenital anomalies. CT may show a gas-filled multicystic mass or a focal area of consolidation (our case). The MR appearance depends on the composition of the malformation and is variable.
- Type 3: Represents an abnormality of the terminal bronchiolar/alveolar duct region. Third most common type (10%). Tiny cysts (< 0.2 cm in diameter). Frequently associated with other congenital anomalies. Associated with maternal polyhydramnios in ~80% of cases. Can involve an entire lobe or the whole lung. The tiny cysts are too small to resolve by CT; therefore, the lesion appears as a solid mass. MR shows a homogeneously T2-hyperintense solid mass with normal adjacent parenchyma.
- Type 4: Represents an abnormality of the distal acinus or alveolar saccular/alveolus region. May or may not be the same thing as pleuropulmonary blastoma. Presents before 4 years of age. Sudden respiratory distress due to tension pneumothorax is a unique feature of this subtype. Imaging reveals a large lesion, usually localized to one lobe, with large air-filled cysts. Mediastinal shift may be out of proportion to the mild/absent symptoms.
The images shown here are from a neonate with a lung mass identified at prenatal ultrasound. The radiograph shows an oval lesion in the left lung base medially, which was confirmed by CT. Biopsy showed a type 2 CPAM.
References
- Daltro P, Werner H, Gasparetto TD, Domingues RC, Rodrigues L, Marchiori E, Gasparetto EL. Congenital chest malformations: a multimodality approach with emphasis on fetal MR imaging. Radiographics. 2010 Mar-Apr;30(2):385-95.
- Kim WS, Lee KS, Kim IO, Suh YL, Im JG, Yeon KM, Chi JG, Han BK, Han MC. Congenital cystic adenomatoid malformation of the lung: CT-pathologic correlation. AJR Am J Roentgenol. 1997 Jan;168(1):47-53.
- Lee EY, Boiselle PM, Cleveland RH. Multidetector CT evaluation of congenital lung anomalies. Radiology. 2008 Jun;247(3):632-48.
- Stocker JT. Congenital pulmonary airway malformation: a new name and an expanded classification of congenital cystic adenomatoid malformations of the lung. Histopathology 2002;41(suppl 2): 424–31.
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