Congenital Pulmonary Airway Malformation

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662649 JDMXXX10.1177/8756479316662649Journal of Diagnostic Medical SonographyPhillips

research-article2016

Case Study

Congenital Pulmonary Airway
Malformation: A Case Study
and Case Comparison

Journal of Diagnostic Medical Sonography
2016, Vol. 32(5) 294 –298
© The Author(s) 2016
Reprints and permissions:
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DOI: 10.1177/8756479316662649
jdms.sagepub.com

Paige Phillips, RDMS, RVT1

Abstract
Congenital pulmonary airway malformation (CPAM) is a rare congenital lung mass of the fetus that can present as solid
or cystic. This is often diagnosed prenatally with sonography and routinely followed through the term of the pregnancy.
Congenital pulmonary airway malformation is now classified into five different types that all originate from different
areas of the lung and can vary in appearance. CPAM does present with a few differentials that need to be assessed,
including bronchopulmonary sequestration, bronchogenic cyst, and congenital diaphragmatic hernia. It is vital to fully
assess the fetal thorax and determine if there are any abnormalities present and if so the originating vasculature. This
case report demonstrates a type 3-CPAM and its sonographic appearance as well as the classifications of CPAM and
the possible differential diagnoses.

Keywords
congenital cystic adenomatoid malformation, CCAM, congenital pulmonary airway malformation, CPAM,
bronchopulmonary sequestration, fetal lung lesion

Introduction

Congenital pulmonary airway malformation (CPAM) is a
benign nonhereditary congenital mass of the lung that can
present as cystic or solid mass.1, 2 This lesion is described
as an overgrowth of terminal bronchopulmonary tissue.3
Congenital cystic lung lesions are rare; however, CPAM is
the most common fetal lung lesion.4 Congenital pulmonary
airway malformation is now classified into five different
types that vary, depending on origin of the mass as well as
presence of cysts, dimensions, and the sonographic appear-
ance.2 This particular lung mass is typically unilateral and
most often discovered in the lower lobes of the lungs.
Bilateral CPAM is rare and is associated with a poor prog-
nosis.5 Congenital pulmonary airway malformation occurs
in approximately 1 in 11 000 to 1 in 35 000 pregnancies.6
The average gestational age for discovery of the lung mass
is 22 weeks. The following case report demonstrates a type
3-CPAM and its associated sonographic appearance.

Case Report

Milwaukee, Wisconsin, USA) ultrasound equipment was
utilized and a curved linear array transducer. The fre-
quency was shifted to 5.2 MHz. The sonogram showed an
echogenic, homogenous, wedge-shaped mass that was
discovered in the area of the fetal thorax, just superior to
the fetal diaphragm (Figure 1).

This patient was sent for a targeted sonogram of the sus-
pected lung lesion. It was discovered during the targeted
sonogram that the lung lesion measured 2.16 × 1.99 × 1.71
cm and was located in the right lower chest (Figures 1
and 2). No mass effect was visualized on surrounding
structures or the vasculature. The mass had no sono-
graphic evidence of cystic architecture. During the tar-
geted sonogram, the vascular origin of the mass was
thoroughly assessed to aid in the diagnosis of this lesion.
It was determined that the mass originated from the pul-
monary vasculature versus the thoracic aorta (Figure 3).
Determining the origin of vascularity helped to differ-
entiate the diagnosis from a CPAM versus a bronchopul-
monary sequestration.7 Interrogating the vascular origin

This case involves a 32-year-old female patient, gravida 5
para 4 with no prior pregnancy complications. The esti-
mated gestational age of this singleton fetus is 21 weeks
and 2 days, based on last menstrual cycle. The patient
presented to the department for a routine anatomy scan of
a 21-week fetus. A General Electric P5 (GE Healthcare,

1El Centro College, Dallas, TX, USA

Received November 25, 2014, and accepted for publication July 13, 2016.

Corresponding Author:
Paige Phillips, RDMS, RVD, El Centro College, 301 N Market St, Dallas,
TX 75202, USA.
Email: paigephillips414@gmail.com

Phillips

295

Figure 1. Sagittal sonographic view of a wedge-shaped
echogenic lesion in the thorax of a 21-week gestational fetus.

Figure 3. Color Doppler interrogation of a wedge-shaped
echogenic lesion in the thorax of a 21-week gestational fetus,
in the sagittal plane.

It additionally allowed for distinguishing where the lesion
arose relative to the bronchial tree.9 The additional clas-
sifications are referred to as type 0 to 4. Therefore, CCAM
is more recently renamed and reclassified to CPAM with
five different distinct categories.9

Based on the Stocker classification, a type 3-CPAM is
the best differential diagnosis for this particular case.2
A follow-up sonogram was ordered for this patient in four
weeks to check the size of the lesion and see if there were
any changes in its sonographic characteristics. Four weeks
later, there were no sonographic changes to the lung
lesion. The patient was asked to come back in four more
weeks for further follow-up. Unfortunately, the patient
discontinued the follow-up appointment, and the mass
could not be observed for any possible regression in size.

Figure 2. Transverse sonographic view of the same
echogenic lesion in the thorax of a 21-week gestational fetus.

Discussion

of the mass allowed the sonographer to discover if the
mass originated from pulmonary vasculature or systemic
vasculature. A CPAM is provided blood flow from the
pulmonary artery. Bronchopulmonary sequestrations
have a blood supply that originates from the thoracic
aorta. Therefore, the vascular origin of the mass should
be thoroughly assessed to differentiate the mass from
other possible pathologies. In 1977, Stocker et al.8 classi-
fied three different types of congenital cystic adenoma-
toid malformation (CCAM). It was broken down into
types 1 to 3. In the year 2002, the Stocker classification
was updated to add two additional classification types
and changed the name from CCAM to CPAM.9 The
update was based on the discovery that there were two
additional classifications of the lung lesion and that not
all of the lesions were cystic or of adenomatoid origin.

Sonography is the gold standard imaging modality for
obstetrics. There are certain situations where other imag-
ing modalities may be useful to aid in a definitive diagno-
sis. In the situation of a CPAM lesion, sonography is the
imaging modality of choice with MRI being an alterna-
tive option.10,11 Sonography is used to determine the size,
shape, echogenicity, circulation origin, and any possible
changes that may occur in the mass throughout the preg-
nancy. A MRI is useful in determining the exact anatomy
of the lung where the pathological process is located. In a
study that was reported by O’Conner et al.,10 sonography
was advocated as a superior imaging choice for demon-
strating the feeding circulation of the mass.8

Congenital pulmonary airway malformation is broken
down into five different types. Type 0 arises from the tra-
chea or the bronchus of the lung, and it is the least com-
mon form of CPAM, occurring in approximately 1% to

296

Journal of Diagnostic Medical Sonography 32(5)

3% of cases. Sonographically, this type will present as a
solid echogenic mass with lungs that are small. This form
of the condition is typically considered lethal. Type
1-CPAM is the most common form and arises from the
distal bronchus or the proximal bronchiole. Fifty percent
to 70% of CPAM cases are type 1. The sonographic
appearance of type 1 is identified as one to a few large
cysts present in the lung mass. Type 2-CPAM comes from
the terminal bronchioles and accounts for approximately
15% to 30% of cases. This type of lesion contains cysts
that are smaller in size and also has solid areas. The
abnormality most associated with other fetal anomalies is
type 2-CPAM. Type 3-CPAM arises from the alveolus
and is rare. This type only occurs in about 5% to 10% of
cases. Sonographically, this type of mass appears as an
echogenic and solid mass because these cysts are micro-
scopic. Type 4 arises from the alveolar and contains mul-
tiple large cysts. This type accounts for 5% to 15% of
CPAM cases. In the past, type 4-CPAM has been associ-
ated with malignancy.12,13

There are a few differential diagnoses to CPAM. The
most important differential diagnosis is a bronchopulmo-
nary sequestration. Bronchopulmonary sequestrations are
nonfunctioning lung tissue masses that are fed by the sys-
temic vasculature. They are usually present in the lower
lobes of the lungs. It can be very difficult to differentiate
CPAM from a pulmonary sequestration. A bronchopul-
monary sequestration appears as a solid, echogenic,
homogenous, well circumscribed mass that can be round
or wedge-shaped sonographically. The most difficult type
of CPAM to differentiate from a pulmonary sequestration
is type 3-CPAM. It is very important to identify the vas-
cular origin of the mass to determine if the mass is fed
from the pulmonary vasculature or if it is fed by systemic
vasculature. Pulmonary sequestration is also associated
with other fetal anomalies. An additional differential
diagnosis to CPAM is a bronchogenic cyst. In a broncho-
genic cyst, abnormal budding occurs during the develop-
ment of the tracheobronchial tree. The least likely
differential diagnosis for this entity is a congenital dia-
phragmatic hernia.2,6,14

A CPAM lesion typically cannot be found with sonog-
raphy until 17 weeks’ gestation.15 When a CPAM is found
sonographically, routine sonograms are performed on the
fetus to closely watch the lung mass. Changes can present
in the mass, and it is important to follow and document
any changes that may occur. It is typical for the mass to
regress in size, and this usually begins to occur between
25 and 28 gestational weeks.7,14,16 Prognosis is going to
depend on the CPAM classification and if there are other
fetal anomalies present.7 A larger sized lesion that does
not regress in size is more likely to lead to a fatal out-
come.17 Hydrops fetalis could develop in the fetus from
the mass compressing other structures; this will typically

require an emergency cesarean section.16 Other possible
fetal anomalies that could be present with type 2-CPAM
are gastrointestinal defects, defects of the abdominal
wall, fetal heart anomalies, and anomalies of the central
nervous system, spine, and kidneys.13

A type 3-CPAM case study was reported by Bennett1
in 2003. The patient was in her early 30s at the time of her
second pregnancy. A sonogram was performed on her
20-week 6-day fetus, and a hyperechoic mass was visual-
ized in the inferior posterior left lung. It was noted that
there were no cystic structures visualized. This was con-
sidered to be most likely a type 3-CCAM, with a possible
differential diagnosis of pulmonary sequestration. This
patient went for MRI, and it was determined that the mass
did not demonstrate any vessels that were originating
from the thoracic aorta. This particular patient had rou-
tine sonograms once a month to follow the progress of the
CCAM lesion. There was a sonogram performed a few
days prior to birth, and the lung lesion was difficult to
image and appeared to be significantly smaller in size
from the original finding. The fetus had a good prognosis
at birth. Although these cases are similar, the 2003 case
could not demonstrate a vascular origin of the mass sono-
graphically. With the quality and resolution of current
ultrasound equipment, it is feasible that it could be easier
to determine the vascular origin of a fetal lung mass.8

An additional fetal lung mass case was reported by
Fulghum and Vasquez.13 This particular case was a case
of triplets with no maternal complications. During a rou-
tine sonogram, a cystic lung mass imaged in the lower
lobe of the left lung of fetus C. Sonographic measure-
ments determined that the cyst was 3 × 4 cm. This lesion
was followed by routine sonography throughout the term
of the pregnancy. There were no further complications
documented throughout the pregnancy, and the lung mass
of fetus C remained unchanged. A chest CT was per-
formed on this infant, and images showed a mass that
covered half of the lower lobe of the left lung. The CT
confirmed what had been discovered sonographically.
Three months later, this infant underwent surgery to
resect the lung mass. Upon pathologic evaluation, it was
determined that the lung mass was CCAM. This case is
another example showing that sonography is a good
imaging modality for identifying fetal lung lesions. This
case differs from the one being reported in that the mass
appeared to have cystic components on the sonogram. A
chest CT was the modality of choice as opposed to the use
of imaging the mass with MRI.10

Based on these descriptive cases, sonographers
should consider the importance of thoroughly assessing
the fetal lungs as part of a routine obstetric sonogram. It
is important to realize that CPAM can present in several
different variations depending on the lesion’s typology.
When performing a sonogram, it is important for the

Phillips

297

Conclusion

Congenital pulmonary airway malformation, once
referred to as CCAM, represents approximately 25% of
congenital lung lesions. CPAM is classified into five
different types depending on origin, cyst presence, and
cyst size. The most common differential diagnosis to
CPAM is the bronchopulmonary sequestration. CPAM
is typically found at around 22 gestational weeks and is
followed up with routine sonography through the term
of the pregnancy. CPAM can vary in sonographic
appearance as well as prognosis depending on the clas-
sification of the lesion. Sonography plays a vital role in
the identification and screening for CPAM. Sonography
and MRI are recommended as imaging modalities for
classifying the type of mass that is present.

Acknowledgments

The author would like to thank Jacqueline Monaco, RDMS,
RVT, El Centro College, and family for their support.

Declaration of Conflicting Interests

The author declared no potential conflicts of interest with respect
to the research, authorship, and/or publication of this article.

The author received no financial support for the research,
authorship, and/or publication of this article.

Funding

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Figure 4. Scheme for categorizing the sonographic
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Note. This diagram is a method for depicting the variety of
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sonographer to image and document the echogenicity of
the fetal lungs and assess for areas of localized increased
echogenicity. If a mass is found in the lung, besides
marking, measuring, and applying color Doppler to the
lesion, it is also important to determine the circulation
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a basis for assessing any changes that may be seen in
follow-up sonograms. Measuring the mass from leading
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– Type 1: cystic with large cysts
– Type 2: cystic and solid with other anomalies
– Type 3: echogenic solid mass
– Type 4: large cystic mass
– Type 0: solid mass with small lungs.

See Figure 4 for a diagram comparing the different types
of CPAM.

298

Journal of Diagnostic Medical Sonography 32(5)

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