CPAM Type 3

Figure 1. CPAM Type 3

A female infant delivered at 27 weeks' gestation because of polyhydramnios and fetal hydrops underwent right middle lobectomy for this solid mass that weighed 59 g (normal for both lungs, 25 g). The infant died shortly after the operation.

Almost the entire lobe is involved by the whitish malformation with scattered small cystic spaces. Some normal parenchyma is present at the top right.

The hydrops is believed to be caused by compression of systemic veins.

Figure 2. Low-Power View

Normal architecture is distorted by cystic bronchiole-like spaces with irregular shapes. A small amount of smooth muscle lies in their walls. The remainder of the parenchyma is composed of canals lined by cuboid epithelium, resembling normal early fetal lung (see below).

Note the large artery, which is not related to an airway, at the upper right and the absence of visible vessels next to the dilated bronchioles.


Figure 3. High-Power View

Here, the cuboid epithelium lining canals is better seen.

This glandular appearance was the basis for "adenomatoid" in the previous name, cystic adenomatoid malformation.


Figure 4. Normal Canalicular Phase of Lung Development

Three stages of lung development have been described: pseudoglandular, canalicular, and saccular. This image is from a 21-week-gestation infant showing the normal architecture of the canalicular phase: non-dilated bronchioles have ciliated, columnar epithelium and distal spaces are lined by cuboid epithelium. Note the resemblance to the type 3 CPAM.

Find the branch of the pulmonary artery adjacent to the bronchiole at the lower right.


Note that type 2 and type 3 CPAMs may have a similar solid appearance with few cysts on gross examination. They differ histologically in the type of epithelium lining the distal air spaces--flat in type 2 CPAMs and cuboid in type 3 CPAMs.

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Branch of pulmonary artery