Text: Yang Qianni Compiled by: Liang Yingxiu
(Kuala Lumpur) Pulmonary malformations are congenital and are related to the formation of fetal lungs. The lungs develop from a pair of lung buds, which grow into the main respiratory tract, trachea, and left and right lobar bronchi (see figure), and continue to branch out into bronchioles and terminal spongy alveoli. Just like a tree grows from a trunk into branches, in this case the bronchial branches and alveoli act like leaves.
Lung malformation refers to a mass formed abnormally in lung tissue.
Covers conditions that affect the airway or lung tissue itself, such as:
◆Congenital pulmonary respiratory malformation
(Congenital Pulmonary Airway Malformation, CPAM),
Formerly known as congenital cystic adenomatoid malformation
(Congenital Cystic Adenomatoid Malformation, CCAM)
◆Broncho-Pulmonary Sequestration (BPS)
◆Congenital Lobar Emphysema (CLE)
Most occur within or outside the lung lobes
Dr Nada Sudhakaran, Consultant Pediatric Surgeon, pointed out that abnormalities at any stage during fetal lung development will lead to different types of lung malformations, but the exact cause of lung malformations is currently unknown.
“If the problem occurs very early, cysts may form instead of normal lungs. These cysts are usually located in the trachea or the left and right main bronchi and are called bronchogenic cysts.”
A common example of an abnormality forming within the lungs is Congenital Pulmonary Airway Malformation (CPAM), which basically means an abnormality in the lung tissue, which can be cystic, which means cysts appear in multiple parts of the lungs; also Can be solid, i.e. the entire area becomes thicker.
“CPAM is caused by abnormalities in the formation of smaller bronchi. It can occur inside or outside the lung lobes. For example, CPAM and CLE occur within the lung lobes, while BPS occurs within the chest or even within the abdomen. Lung malformations within or outside the lobes.”
He said that the formation of broncho-pulmonary sequestration (BPS) may originate from a lung bud that forms outside the left and right lungs. The tissue formed by this extra lung bud is completely separated from the normally developing lung and is not connected to the trachea, but moves downward toward the diaphragm. If it is contained in the basal lobe, it is an intralobar type; if not, it is an extralobar type.
“Unlike normal lungs, which are supplied with blood flow by the pulmonary artery, most BPS’s blood supply originates from the aorta of the heart. In addition, it is not connected to the trachea and cannot be filled with gas, so it is a solid piece of tissue. This is BPS main features.”
“Approximately 1 in every 20,000 to 30,000 children will suffer from lung malformations, and the vast majority of them are CPAM. There is no gender difference in CPAM. 95% of cases affect a single lung lobe (lobe), and less than 3% are It affects both lobes of the lung. In contrast, CPAM usually affects the lower lobes and CLE affects the upper lobes.”
The trachea is loose and unable to drain fluids
He pointed out that each person’s main trachea, bronchi and bronchioles are surrounded by a hard ring of cartilage that prevents these tubes from collapsing. The hypothesized theory for the formation of cystic CPAM is that in the stage before alveolar formation, the trachea connected to the lung segments or lobes is relatively floppy due to the lack of good cartilage support.
During this period, the fetus “inhales” amniotic fluid into the developing lungs. However, due to the softness of the trachea, the fluid cannot be easily discharged, and normal alveoli cannot be formed. Instead, fluid accumulation and cysts occur.
The same theory applies to CLE, but it occurs at a stage after alveoli are formed. With both conditions, once the baby is born and starts breathing air, the fluid is replaced by air.
As for the solid type of CPAM, it is thought to be an abnormal overgrowth of bronchiolar tissue that forms solid tissue rather than tubes, and does not form alveolar tissue. They are not cystic because there are no tubes to introduce amniotic fluid or air into these abnormal areas.
Combination of large and small cysts
Anatomy Category 5 Pulmonary Malformations
With more advanced ultrasound machines available to obstetricians and fetal medicine specialists, congenital pulmonary airway malformations (CPAM) are by far the most common and detected cases.
These lesions may consist of many tiny cysts (microcystic), a few large cysts (macrocytic), a combination of both, or with solid tissue.
Accompanied by other abnormal diseases
CPAM is mainly divided into 5 types, namely I, II, III, 0 and IV.
Type I CPAM is the most common, accounting for approximately 65% of all CPAM, and consists of single or multiple cysts greater than 2 cm in diameter. Typically they occupy no more than one lobe of the lung and are asymptomatic at birth. Due to the accumulation of mucus in these cysts, there is a risk of lung infection, which is approximately 5%.
The lifetime risk of malignant transformation is estimated to be approximately 3%.
Type II is also the second most common type of all CPAM cases, accounting for 15% to 20%. Its cysts are smaller, less than 2 centimeters in diameter, so the risk of infection is smaller and there is no quantifiable risk of malignant transformation.
However, some children may have other abnormalities, such as kidney or heart abnormalities that can cause symptoms.
Type III CPAM accounts for approximately 5% to 10% of all cases. These are usually large, noncystic lesions that can compress or push against other organs (such as the heart) or other normal lobes of the lungs. Due to this compression, the lesion can push the esophagus, making the fetus unable to swallow amniotic fluid, causing polyhydramnios, or the heart is compressed and causes fluid accumulation.
Type 0 is rare and difficult to survive
After birth, it may also compress good lungs and cause a decrease in lung function. The risk of malignant transformation is negligible.
Type 0 CPAM is very rare, accounting for less than 2% of total cases. They usually involve the entire lung on one side and have small, firm lungs. Usually difficult to survive after birth. No associated risk of malignant transformation has been observed.
Type IV occurs in up to 10% of CPAM cases. They are large cysts more than 10 cm in diameter and are usually located on the surface of the lungs. Symptoms include postpartum infection or pneumothorax, and the risk of malignant transformation is about 5%.