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Congenital lung cysts

Ch'in and Tang first described cystic adenomatoid malformation (CAM) as a distinct entity in 1949. CAM is a developmental hamartomatous abnormality of the lung with adenomatoid proliferation of cysts resembling bronchioles. CAM represents approximately 25% of all congenital lung lesion. CAM is believed to result from focal arrest in fetal lung development before the seventh week of gestation secondary to a variety of pulmonary insults. CAM is subdivided into 3 major types.

	Type I	Type II	Type III
Morphology	Multiple large cysts or single large cyst	Multiple, evenly spaced cysts not over 1.2 cm	Multiple small cysts less than 0.5 cm
Contents	Air or fluid	Air	Solid
Wall	Smooth muscle and connective tissue	Terminal bronchioles	Adenomatoid hyperplasia or bronchial

B. Symptoms
· Progressive respiratory distress in a newborn infant
· Tachypnea, subcostal retraction, cyanosis

CT findings

Areas of small cysts (<2 cm in diameter) appearing with other abnormalities (a larger cystic area, consolidation, or low attenuation) are the most frequent findings.
Multiple large cystic lesions (>2 cm in diameter) are seen alone or with other abnormalities (areas of small cysts, consolidation, or low attenuation).
Low-attenuation areas are clusters of microcysts