Cystic Adenomatoid Malformation 

Updated: Dec 08, 2015
Author: Anne E Stone, MD; Chief Editor: Michael R Bye, MD 

Overview

Background

Congenital cystic adenomatoid malformation (CCAM) is a rare abnormality of lung development. CCAM is a type of congenital thoracic malformation and refers to a group of malformations of the airways. There are different types of lesions (types 0-4), some associated with cystic areas and adenomatous overgrowth of the terminal bronchioles.[1, 2]

The routine use of prenatal ultrasonography has led to frequent prenatal diagnosis and has provided great insight into the natural history of CCAM. Improvements in surgical techniques (ie, both prenatal and postnatal) as well as greatly enhanced imaging modalities have altered the surgical approach to this lesion.

Pathophysiology

The pathophysiologic effects of CCAM may be divided into prenatal and postnatal effects. Large lesions may be associated with the development of hydrops fetalis in as many as 40% cases and is a poor prognostic sign. Hydrops is thought to arise from compression of the inferior vena cava, which compromises venous return and leads to a decrease in cardiac output and the development of effusions. Fetal demise may result; premature delivery is attempted in order to salvage the fetus.[3] The other main prenatal event is compromised pulmonary growth. Resultant pulmonary hypoplasia may lead to the postnatal development of respiratory distress.

Polyhydramnios has also been associated with CCAM. This develops as a result of elevated intrathoracic pressure that leads to esophageal compression and the inability to swallow.[4]

CCAM may remain undiagnosed until it is discovered as an incidental finding later in life; however, its usual postnatal presentation is respiratory distress in the newborn period. This may be due to pulmonary hypoplasia, mediastinal shift, spontaneous pneumothorax, and pleural effusions secondary to hydrops. Recurrent chest infections may be a feature later in life.[5] A risk of malignant transformation in later years is noted.[6]

Prenatal regression and complete prenatal resolution have also been described.[6, 7, 8]

Epidemiology

Frequency

United States

No data are available regarding the frequency of this lesion; however, it is a rare condition.

International

A review of 48 cases from 5 centers in Canada led to an estimated incidence of 1:25,000 to 1:35,000 of patients who were prenatally diagnosed.[7] The use of prenatal ultrasonography has led to an increase in prenatal diagnosis.

Mortality/Morbidity

Most series report a mortality rate of 25-30% of all children who present in the newborn period with CCAM; however, these figures do not include asymptomatic children who present later in life. Furthermore, the use of elective abortion may lead to an underestimation of perinatal mortality by preferentially terminating fetuses with a higher risk of mortality. The reported mortality rate of prenatally diagnosed CCAMs ranges from 9-49%. Reviews of children who are asymptomatic in the neonatal period with antenatally diagnosed lesions suggest that 3-10% will develop symptoms in the first year of life.[9, 10] A more recent study suggested that 18 of 21 patients developed symptoms at a median age of 2 years.[11]

Risk factors for a poor outcome include hydrops fetalis.[3, 7] Other indicators of poor prognosis include the type of lesion; microcystic CCAM is associated with much poorer outcomes.[7, 12]

The overall size of the lesion has also been reported as being an important predictor of survival;[13, 14] however, this index may be compromised by the fact that CCAM may decrease in size or even resolve over time in utero.[7] The major morbidity is related to pulmonary compromise. A large lesion may be associated with pulmonary hypoplasia.[10] This can cause respiratory distress at birth.

Some authorities have suggested that the presence of bilateral lesions is associated with a worse outcome. More controversially, left-sided lesions may be associated with a greater mortality rate than right-sided lesions.

One study suggested that polyhydramnios is also associated with a poorer outcome.

The potential for malignant transformation is recognized in all cases of CCAM.[6, 15, 16] Whether or not complete resection of the affected area completely removes this risk is not known.

Other complications that have been described include the development of spontaneous pneumothorax, hemopneumothorax, and associated hemoptysis.[7]

Age

CCAM is a congenital condition. Cases are typically identified prenatally by routine ultrasonography screening.[7] Most postnatally identified cases present in the newborn period. CCAM may present in the older child and adult as an incidental finding or secondary to repeated infection.[17, 5, 18]

 

Presentation

History

With the increasing use of prenatal ultrasonography as well as improvement in technology and skill, most cases of congenital cystic adenomatoid malformation (CCAM) are prenatally diagnosed. Prenatally diagnosed lesions can present with various symptoms.

  • Respiratory distress[17]

    • This is the presenting symptom in most newborns with a diagnosis of CCAM. It may range in severity from grunting, tachypnea, and a mild oxygen requirement to fulminant respiratory failure requiring aggressive ventilator support or extracorporeal membrane oxygenation (ECMO).

    • Multiple mechanisms account for the onset of respiratory difficulty. Pulmonary hypoplasia may arise as a consequence of a large CCAM, mediastinal shift may compromise cardiac and respiratory function, spontaneous pneumothoraces may occur, and air trapping within the cyst leads to compression of functional pulmonary tissue.

  • Recurrent infection: Children in whom the CCAM has not been resected are at risk of recurrent pulmonary infections due to bronchial compression, air trapping, and inability to clear secretions.

  • Hemoptysis: Hemoptysis has occasionally been described as a manifestation of CCAM in the older child.

  • Dyspnea and chest pain: Dyspnea may be a feature of pneumothorax, which has been described as a presenting feature of CCAM.

  • Miscellaneous: Cough, fever, and failure to thrive have all been reported in association with the presentation of CCAM.

Physical

Generally, the physical signs observed in children with CCAM are nonspecific.

  • Tachypnea: Tachypnea is the most common sign encountered in the newborn period, reflecting respiratory distress.

  • Pneumothorax/air trapping: Signs consistent with a pneumothorax or air trapping may be elicited, including tracheal deviation, which indicates mediastinal shift, shifted heart sounds, and decreased air entry on the affected side.

  • Cyanosis

  • Accessory muscle use

  • Grunting

  • Failure to thrive

Causes

The cause of CCAM is not understood.

  • Resected CCAMs show signs of increased cell proliferation and decreased apoptosis.[1, 19]

  • Studies have investigated the role of HOXB5 gene and protein expression, as well as other growth factors such as mesenchymal platelet–derived growth factor-BB.[20, 21, 22]

 

DDx

 

Workup

Laboratory Studies

See the list below:

  • Laboratory studies are generally not helpful in the diagnosis of congenital cystic adenomatoid malformation (CCAM).

  • Perform routine karyotyping on all amniotic fluid obtained from the child after birth; however, incidence of chromosomal anomalies associated with CCAM is extremely low.

Imaging Studies

See the list below:

  • Chest radiography is essential in the workup of the child with suspected CCAM.[23, 24] See image below.

    The CT scan of the chest reveals a right lower lob The CT scan of the chest reveals a right lower lobe congenital cystic adenomatoid malformation (CCAM) in a 6-week-old infant who presented with tachypnea. The most striking feature is the solitary enlarged cyst surrounded by numerous microcysts. This lesion was resected without complication.

    See the list below:

    • Chest radiography almost invariably identifies CCAM of sufficient size to cause clinical problems.

    • The usual appearance is of a mass containing air-filled cysts.

    • Other radiological signs that may be evident include mediastinal shift, pleural and pericardial effusions, and pneumothoraces. The diagnosis may not be clear from chest radiography alone. Chest radiography may reveal a mass without any evidence of cysts.

    • In cases in which the cystic lesion involutes, chest radiography may not allow sufficient definition to determine whether the CCAM has completely disappeared.

  • CT scanning[25]

    • CT scanning of the thorax provides a safe and rapid means of defining the extent of CCAM in all age groups.

    • The typical appearance is of multilocular cystic lesions with thin walls surrounded by normal lung parenchyma. The presence of superimposed infection with the lesion may complicate the appearance.

    • Air fluid levels may be evident.

    • CT scanning of the chest may outline additional coexisting lesions. Series have suggested a small percentage of cases thought to have resolved antenatally that demonstrated persistence of lesions on CT scan.

    • The definition of high-resolution chest tomography (HRCT) is sufficient to differentiate between microcystic and macrocystic lesions.

  • Prenatal ultrasonography[3, 26]

    • With increasing use and technical ability of prenatal ultrasonography and sonographers, most cases of congenital lung anomalies are prenatally diagnosed. No specific diagnostic features of CCAM allow the ability to distinguish it unequivocally from other lung lesions such as congenital lobar emphysema or pulmonary sequestration.

    • Ultrasonography may demonstrate evidence of hydrops, such as fetal ascites or pleural effusions.

    • Type I lesions (see Histologic Findings) appear as multiple large cystic areas in the lung. In type II lesions, multiple small cysts are evident on ultrasonography. Because of the extremely small size of the cysts in type III lesions, the prenatal ultrasonographic appearance is often one of a homogenous mass.

  • MRI[27, 28]

    • MRI permits increased definition of a particular lesion, thereby enhancing the clinician's ability to accurately diagnose and offer an informed prognosis.

    • Additionally, maternal problems that prevent the optimal use of fetal ultrasonography, such as obesity, poor fetal lie, and oligohydramnios, pose no obstacle to MRI. MRI may be useful particularly in distinguishing CCAM from congenital diaphragmatic hernia.

    • Lastly, no maternal or fetal exposure to ionizing radiation occurs in contrast to the use of CT scanning.

  • Other imaging studies

    • Perform renal and cerebral ultrasonography in all newborns with CCAM in order to exclude coexisting renal and CNS anomalies.

    • Perform echocardiography in all newborns with CCAM to rule out any coexisting cardiac lesions. Furthermore, in infants with respiratory distress, echocardiography may provide evidence of persistent pulmonary hypertension (eg, right-to-left shunting, increased pulmonary artery pressures).

Procedures

See the list below:

  • Amniocentesis may be indicated to obtain amniotic fluid for karyotyping.

Histologic Findings

CCAM has been described as a hamartoma, namely, abnormal tissue with an excess of one or more tissue components. CCAMs generally communicate with the bronchial tree and derive their blood supply from the pulmonary circulation, in contrast to pulmonary sequestration, which derives its blood supply from the aorta.[4]

In 1977, Stocker grossly classified CCAM into 3 types based mostly on cyst size, as follows:

  • Type I includes multiple large cysts (>2 cm in diameter) or a single large cyst surrounded by numerous smaller cysts. Type I is the most common type of CCAM and is associated with an excellent prognosis.[12]

  • Type II CCAM has multiple small cysts, usually less than 1 cm in diameter, and accounts for over 40% of cases of CCAM. In Stocker's series, as many as 60% of type II lesions are associated with other congenital anomalies that may affect prognosis, specifically renal agenesis.[12]

  • Type III CCAMs are large and account for less than 5% of all cases. They consist of multiple microcysts, measuring less than 0.5 cm in diameter.[12]

In 1993, Adzick reported his group system of classification. Microcystic lesions (cysts measuring < 5 mm) were usually associated with fetal hydrops and, hence, a poor prognosis. Macrocystic lesions (ie, cysts >5 mm) were not usually associated with hydrops and had a good prognosis.[3]

More recent classification divides lesions into 5 types (0-5) of pulmonary airway malformations based on the site of the tracheobronchial/acinar structures where malformation developed. Type 0 refers to acinar atresia (a tracheobronchial defect) and type 4 has multiple cysts lined by flattened epithelium (an alveolar defect).[2, 29]

Other Tests

A study by Barikbin et al reported that postnatal lung function tests can detect and monitor congenital cystic adenomatoid malformation and that these tests represent an additional tool to support the decision for or against surgical intervention.[30]

 

Treatment

Medical Care

No specific medical therapies are described for congenital cystic adenomatoid malformation (CCAM), aside from antibiotics in children with CCAM complicated by pneumonia and supportive care, ranging from oxygen supplementation to mechanical ventilation, in older children with respiratory distress.

Surgical Care

Surgical intervention is the mainstay of therapy for CCAM including fetal surgery and postnatal surgical approaches.

  • Fetal intervention

    • Fetal surgery should be considered in patients with large CCAMs and in cases complicated by hydrops, in which prognosis is poor.[3]

    • Thoracocentesis allows drainage of a large cyst with immediate decompression of the CCAM; however, fluid rapidly reaccumulates, thus negating the benefit of the procedure.[3]

    • Another option is to place a thoracoamniotic shunt that continually drains fluid from the CCAM to the amniotic space. This is most beneficial when the CCAM consists of a large fluid-filled cyst. Complications such as obstruction and shunt dislodgement may occur.[3]

    • Resection of the affected lobe (lobectomy) is an alternative procedure for cases with no dominant cyst available for draining. Fourteen cases treated with maternal-fetal surgery from the Children's Hospital of Philadelphia suggest a 50% survival rate from the time of surgical intervention to infant discharge from the neonatal intensive care unit (NICU).[26] Complications included intraoperative bradycardia, the development of preterm labor and maternal mirror syndrome requiring early delivery, and postoperative intrauterine death. Survivors demonstrated residual lung growth and normal development.

  • Postnatal surgery: Resection of CCAM in all children is recommended to remove the risk of direct complications, such as recurrent infection and pneumothorax. Additionally, the malignant potential of CCAM in later life has long been recognized.[16, 4] Children with asymptomatic CCAM that was diagnosed antenatally can be followed without surgical intervention as some lesions may decrease in size or resolve without intervention. If surgery is recommended, most suggest it be completed before the child is aged 12 months to enhance compensatory lung growth. Studies have not confirmed this hypothetical difference in lung function by age at time of surgical resection.[2]

  • Older patients: In one third of cases, the presence of pneumonia indicates the need for more extensive pulmonary resection.[31]

Consultations

See the list below:

  • Fetal surgeon: Referral to a facility with expertise in fetal surgery is warranted for all fetuses diagnosed with CCAM and hydrops. The indications for referral of other affected pregnancies without hydrops are less clear[4] .

  • Pediatric surgeon: If fetal surgery is not indicated, close collaboration with a pediatric surgeon is essential because postnatal resection of the CCAM is necessary. Rarely, respiratory failure resulting from the CCAM may be severe enough to require treatment with ECMO.

  • Neonatologist: Regardless of whether fetal surgery has been performed, delivery of the affected fetus in a tertiary level facility is essential to optimize outcome and minimize complications arising as a result of CCAM.

Diet

No specific diet is necessary.

Activity

Generally, activity is not limited. Patients with an unresected CCAM (who are at risk of pneumothorax) should not partake in any activity that may put them at risk of developing a pneumothorax (eg, diving, unpressurized air travel).

 

Medication

Medication Summary

Antibiotics are necessary in cases with recurrent pneumonia. Otherwise, no medications are specifically indicated for therapy of congenial cystic adenomatoid malformation (CCAM).

 

Follow-up

Further Outpatient Care

See the list below:

  • Generally, following resection of the CCAM, anticipate full recovery.

  • Regular follow-up in patients who present after adolescence may be necessary in order to detect the presence of an associated malignancy.[15, 16]

  • In patients who underwent fetal surgery or postnatal resection of CCAM, no clinical evidence of respiratory problems is anticipated; however, a small study has shown that a slight reduction in lung volumes occurred in children who had CCAM postnatally resected.[7, 32] Few reports of long-term outcomes are available.

Further Inpatient Care

See the list below:

  • Respiratory support may be required before and after resection of the congenital cystic adenomatoid malformation (CCAM).

  • Complications arising as a result of the surgery must be treated (eg, bleeding, infection, analgesia).

Inpatient & Outpatient Medications

See the list below:

  • Antibiotics are necessary in cases with recurrent pneumonia. Otherwise, no medications are specifically indicated for therapy of CCAM.

Transfer

See the list below:

  • Transfer is indicated in cases of CCAM with hydrops to a facility with expertise in fetal surgery.

  • Deliver the baby in a level III NICU.

  • If the infant is delivered in a facility unskilled in the management of critically ill neonates or in cases of CCAM undiagnosed in the antenatal period, transfer these infants to a facility with expertise in neonatology and neonatal surgery.

  • Additionally, the receiving institution should have the capability to offer ECMO.[4]

Deterrence/Prevention

See the list below:

  • As with all children, particularly those with a history of pulmonary problems, avoid smoking by and around the child.

  • In the absence of any known risk factors for the development of CCAM, no advice regarding prepregnancy preventive measures can be provided.

Complications

See the list below:

  • Fetal death caused by hydrops, fetal surgery, prematurity, or associated malformations

  • Premature delivery due to polyhydramnios.

  • Respiratory distress due to hydrops, pulmonary hypoplasia, pulmonary hypertension, pneumothorax, or prematurity

  • Postnatal death due to respiratory distress, untreated hydrops, or pulmonary hypertension

  • Recurrent pneumonia[17]

  • Pneumothorax

  • Hemothorax

  • Malignant change: Rhabdomyosarcoma, pulmonary blastomas, minute squamous cell carcinoma, and bronchioloalveolar carcinoma have all been described in association with CCAM.[15, 16]

Prognosis

See the list below:

  • The risk of mortality in fetuses with hydrops is high.[3]

  • Other indicators of poor prognosis include the type of lesion, with microcystic CCAM associated with much poorer outcomes.[3]

  • The overall size of the lesion has also been reported as being an important predictor of survival; however, this index may be compromised by the fact that CCAM may undergo involution and even disappear in utero.[14, 33]

  • Polyhydramnios is also associated with a poorer outcome.[3]

Patient Education

See the list below:

  • Fully inform the parents of an affected fetus and discuss the prognosis and natural history of this condition, including the possibility of fetal demise, postnatal respiratory failure, and need for surgery and its attendant complications.

  • Discourage prenatal and postnatal smoking.

  • In children who have had an uncomplicated resection of CCAM, no residual effects (based on currently available data) are anticipated.

  • Less data are available regarding the longer-term outcomes in children who underwent fetal surgery.