Fetal Pulmonary Malformations: Defining Histopathology

Defining the spatial landscape of KRAS mutated congenital pulmonary airway malformations: a distinct entity with a spectrum of histopathologic features

The potential pathogenetic mechanisms underlying the varied morphology of congenital pulmonary airway malformations (CPAMs) have not been molecularly determined, but a subset have been shown to contain clusters of mucinous cells (MCC). These clusters are believed to serve as precursors for potential invasive mucinous adenocarcinoma, and they are associated with KRAS codon 12 mutations. To assess the universality of KRAS mutations in MCCs, we sequenced exon 2 of KRAS in 61 MCCs from 18 patients, and we found a KRAS codon 12 mutation in all 61 MCCs. Furthermore, all MCCs from a single patient always had the same KRAS mutation, and the same KRAS mutation was also found in non-mucinous lesional tissue. Next generation sequencing of seven MCCs showed no other mutations or copy number variations. Sequencing of 46 additional CPAMs with MCCs revealed KRAS mutations in non-mucinous lesional tissue in all cases. RNA in situ hybridization confirmed widespread distribution of cells with mutant KRAS RNA, even extending outside of the bronchiolar type epithelium. We identified 25 additional CPAMs with overall histologic architecture similar to CPAMs with KRAS mutations but without identifiable MCCs, and we found KRAS mutations in 17 (68%). The histologic features of these KRAS mutated CPAMs included type 1 and type 3 morphology, as well as lesions with an intermediate histologic appearance, and analysis revealed a strong correlation between the specific amino acid substitution and histomorphology. These findings, together with previously published model organism data, suggests that the formation of type 1 and 3 CPAMs is driven by mosaic KRAS mutations arising in the lung epithelium early in development and places them within the growing field of mosaic RASopathies. The presence of widespread epithelial mutation explains late metastatic disease in incompletely resected patients and reinforces the recommendation for complete resection of these lesions.

A retrospective clinical analysis of 20 cases of congenital lung masses

BACKGROUND

Congenital-pulmonary-airway-malformation (CPAM) and bronchopulmonary-sequestration (BPS) are rare conditions. The objective of this study was to describe the sonographic characteristics and prenatal course of fetal lung mass.

METHODS

A retrospective study on 20 pregnancies with CPAM and BPS diagnosed during 2018-2018 was performed. Data evaluated included gestational age (GA) at diagnosis, size of lesion, CPAM-volume-ratio (CVR), associated sonographic findings and pregnancy outcome.

RESULTS

Fourteen cases of CPAM and six cases of BPS were evaluated. The average GA at diagnosis was 22 weeks'-gestation (range 17-26). 66% were macrocystic-multicystic. Five cases of BPS (71.4%) had other structural anomalies. None of the fetuses with CPAM had additional anomalies. Four pregnancies (20%) underwent termination due to severe hydrops fetalis. Two cases of CPAM (15%) had spontaneous resolution by 30 week's-gestation; three cases (20%) continued to grow during pregnancy and all the rest reached their largest size at 25-28 week's-gestation. Most cases delivered at term (average 37.6 range 32.2-41.4). Two children had lobectomy at 11 and 12 months of life.

CONCLUSIONS

Careful follow-up during pregnancy may result in term delivery of adequate-for-gestational-age newborns, with no need for admission to the NICU, with only 10% need for lobectomy during the first year of life.

Mucinous Cell Clusters in Infantile Congenital Pulmonary Airway Malformations Mimic Adult Mucinous Adenocarcinoma But Are Not Associated With Poor Outcomes When Appropriately Resected

Congenital pulmonary airway malformations (CPAMs) are abnormalities of the lung arising during development. At our institution the majority of type I infantile CPAMs contain mucinous cell clusters (MCCs). The overlapping histology of MCCs and adult in situ mucinous adenocarcinomas, as well as reports of metastatic mucinous adenocarcinoma arising in CPAMs resected later in childhood raise concerns about the malignant potential of these cells. However, after adequate surgical resection, malignant recurrence has not been reported in infants with CPAMs. Despite benign behavior, MCCs often have histologic features that, in an adult, would be consistent with a diagnosis of adenocarcinoma. Therefore, to assess the spectrum of features that may be seen in these presumed precursor lesions, we characterized the histology of 671 MCCs spread across 44 infantile CPAMs and compared them to 10 adult mucinous adenocarcinomas. MCCs in CPAMS were often numerous, widespread, and located outside of the large cysts. Mucinous and nonmucinous epithelium within CPAMs showed complex architecture, making application of adult adenocarcinoma architectural patterns difficult. The MCCs within CPAMs displayed nuclear features similar to adult mucinous adenocarcinomas. The proliferative index in infantile MCCs was higher than in adult mucinous adenocarcinomas but was also higher in uninvolved infantile lung tissue. This work illustrates that histologic features typically associated with adenocarcinoma frequently occur within CPAMs; however, this does not alter their benign behavior. Therefore, extreme caution should be used if adult lung cancer terminology is applied to avoid significant potential psychological and physical harms associated with the label of adenocarcinoma.

Congenital Cystic Lung Lesions: Redefining the Natural Distribution of Subtypes and Assessing the Risk of Malignancy

Asymptomatic cystic lung lesions-congenital pulmonary airway malformations (CPAMs), sequestrations, and bronchogenic cysts-are commonly diagnosed prenatally. Indications to resect are to eliminate risk of malignancy or infection. CPAMs consist of a spectrum of malformations, with type 1 historically considered the most common. Mucinous cell clusters, seen almost exclusively in type 1, are premalignant lesions at risk for progression to mucinous adenocarcinoma. We reviewed and classified 2.5 years of consecutive, prenatally diagnosed lesions as extralobar sequestration, intralobar sequestration, type 1 CPAM, type 2 CPAM/bronchial atresia, or "other" to determine the distribution of lesion types and risk of malignancy. One hundred eighty-four lesions in 174 patients showed type 1 CPAM to be least common subtype. Type 1 CPAMs had more severe presentation, infrequently had features of obstruction, and usually had cysts ≥2 cm. Fifteen of eighteen type 1 CPAMs had mucinous cell clusters (total risk, 8%), with mucous cells outside main cyst in 12/15. No pleuropulmonary blastomas were identified. Additional historic cases were reviewed to further evaluate risk of malignancy. Over 14 years, 28 infants with fetal/type 1 lesions were identified, with clusters of mucinous cells in 75% of cases. A total of 9 pleuropulmonary blastomas were diagnosed in 6 patients over 16 years. Contrary to historical studies, type 1 CPAMs are much less common than type 2, likely related to detection of asymptomatic lesions prenatally. A majority of type 1 CPAMs contain mucinous cell clusters. This data is useful in management of patients in centers that do not resect asymptomatic lesions.

Obstetric and neonatal outcomes in pregnancies complicated by fetal lung masses: does final histology matter?. J Matern Fetal Neonatal Med 2019;34:3662-3668. [PMID: 31722592 DOI: 10.1080/14767058.2019.1689559]

Purpose: Fetal lung masses complicate approximately 1 in 2000 live births. Our aim was to determine whether obstetric and neonatal outcomes differ by final fetal lung mass histology.Materials and methods: A review of all pregnancies complicated by a prenatally diagnosed fetal lung mass between 2009 and 2017 at a single academic center was conducted. All cases included in the final analysis underwent surgical resection and histology diagnosis was determined by a trained pathologist. Clinical data were obtained from review of stored electronic medical records which contained linked maternal and neonatal records. Imaging records included both prenatal ultrasound and magnetic resonance imaging. Fisher's exact test was used for categorical variables and the Kruskal-Wallis test was used for continuous variables. The level of significance was p<.05.Results: Of 61 pregnancies complicated by fetal lung mass during the study period, 45 cases underwent both prenatal care and postnatal resection. Final histology revealed 10 cases of congenital pulmonary airway malformation (CPAM) type 1, nine cases of CPAM type 2, and 16 cases of bronchopulmonary sequestration. There was no difference in initial, maximal, or final CPAM volume ratio between groups, with median final CPAM volume ratio of 0.6 for CPAM type 1, 0.7 for CPAM type 2, and 0.3 for bronchopulmonary sequestration (p = .12). There were no differences in any of the maternal or obstetric outcomes including gestational age at delivery and mode of delivery between the groups. The primary outcome of neonatal respiratory distress was not statistically different between groups (p = .66). Median neonatal length of stay following delivery ranged from 3 to 4 days, and time to postnatal resection was similar as well, with a median of 126 days for CPAM type 1, 122 days for CPAM type 2, and 132 days for bronchopulmonary sequestration (p = .76).Conclusions: In our cohort, there was no significant association between histologic lung mass subtypes and any obstetric or neonatal morbidity including respiratory distress.

Time-lapse Imaging of Alveologenesis in Mouse Precision-cut Lung Slices

Alveoli are the gas-exchange units of lung. The process of alveolar development, alveologenesis, is regulated by a complex network of signaling pathways that act on various cell types including alveolar type I and II epithelial cells, fibroblasts and the vascular endothelium. Dysregulated alveologenesis results in bronchopulmonary dysplasia in neonates and in adults, disrupted alveolar regeneration is associated with chronic lung diseases including COPD and pulmonary fibrosis. Therefore, visualizing alveologenesis is critical to understand lung homeostasis and for the development of effective therapies for incurable lung diseases. We have developed a technique to visualize alveologenesis in real-time using a combination of widefield microscopy and image deconvolution of precision-cut lung slices. Here, we describe this live imaging technique in step-by-step detail. This time-lapse imaging technique can be used to capture the dynamics of individual cells within tissue slices over a long time period (up to 16 h), with minimal loss of fluorescence or cell toxicity.

Live imaging of alveologenesis in precision-cut lung slices reveals dynamic epithelial cell behaviour

Damage to alveoli, the gas-exchanging region of the lungs, is a component of many chronic and acute lung diseases. In addition, insufficient generation of alveoli results in bronchopulmonary dysplasia, a disease of prematurity. Therefore visualising the process of alveolar development (alveologenesis) is critical for our understanding of lung homeostasis and for the development of treatments to repair and regenerate lung tissue. Here we show live alveologenesis, using long-term, time-lapse imaging of precision-cut lung slices. We reveal that during this process, epithelial cells are highly mobile and we identify specific cell behaviours that contribute to alveologenesis: cell clustering, hollowing and cell extension. Using the cytoskeleton inhibitors blebbistatin and cytochalasin D, we show that cell migration is a key driver of alveologenesis. This study reveals important novel information about lung biology and provides a new system in which to manipulate alveologenesis genetically and pharmacologically.

The process of alveologenesis is incompletely understood, partly due to the lack of applicable real-time imaging methods. Here the authors describe the process of alveologenesis and the behaviour of epithelial cells in real-time, using widefield microscopy and image deconvolution in precision-cut lung slices, revealing the dominant role of epithelial cell migration.

The rare solid fetal lung lesion with T2-hypointense components: prenatal imaging findings with postnatal pathological correlation

BACKGROUND

At fetal MR, congenital lung lesions are usually T2 hyperintense with respect to normal lung parenchyma. Some lesions, however, demonstrate unusual patterns of T2 hypointensity, sometimes in a rosette-like pattern. These lesions usually present a diagnostic conundrum.

OBJECTIVE

To evaluate the imaging findings and pathological characterization of fetal solid lung lesions with elements showing T2-hypointense signal with respect to lung.

MATERIALS AND METHODS

This is a retrospective study of lung lesions with elements showing T2 hypointensity treated prenatally and postnatally at our center and with available pathological evaluation. Prenatal imaging evaluation included US and MR; postnatal evaluation consisted of pathological examination of the lesion. We also performed prenatal and postnatal chart review.

RESULTS

Six cases met study criteria. Areas of decreased echogenicity/T2-hypointense signal were more conspicuous at MR than US. At pathology, these areas correlated with immature parenchymal development and increased mesenchymal tissue. Five of these lesions were congenital pulmonary airway malformations (CPAM); one was a congenital peribronchial myofibroblastic tumor (CPMT). The lesions did not significantly change in size after steroid administration. They were all large in volume and were associated with increased amniotic fluid. All cases of CPAM underwent premature delivery (one of them weeks after fetal surgical resection of the lesion for worsening hydrops); the fetus with CPMT was delivered at term. The neonate with CPMT succumbed shortly after birth secondary to lung hypoplasia; the remaining five neonates survived.

CONCLUSION

The differential diagnoses of prenatal lung lesions that contain unusual T2-hypointense elements include CPAM and CPMT. The T2-hypointense areas appear to correlate with increasing degree of immaturity at histology. None of the lesions significantly changed in size after prenatal administration of steroids. All cases with CPAM lesions did well despite persistent polyhydramnios and premature birth. The single case of CPMT, however, resulted in neonatal demise shortly after birth secondary to pulmonary hypoplasia. It is important that fetal radiologists, obstetricians and fetal surgeons alike are aware of these lesions so that appropriate diagnosing and parental counseling can be reached.

Congenital pulmonary airway malformations: state-of-the-art review for pediatrician's use

Congenital pulmonary airway malformations or CPAM are rare developmental lung malformations, leading to cystic and/or adenomatous pulmonary areas. Nowadays, CPAM are diagnosed prenatally, improving the prenatal and immediate postnatal care and ultimately the knowledge on CPAM pathophysiology. CPAM natural evolution can lead to infections or malignancies, whose exact prevalence is still difficult to assess. The aim of this "state-of-the-art" review is to cover the recently published literature on CPAM management whether the pulmonary lesion was detected during pregnancy or after birth, the current indications of surgery or surveillance and finally its potential evolution to pleuro-pulmonary blastoma.

CONCLUSION

Surgery remains the cornerstone treatment of symptomatic lesions but the postnatal management of asymptomatic CPAM remains controversial. There are pros and cons of surgical resection, as increasing rate of infections over time renders the surgery more difficult after months or years of evolution, as well as risk of malignancy, though exact incidence is still unknown. What is known: • Congenital pulmonary airway malformations (CPAM) are rare developmental lung malformations mainly antenatally diagnosed. • While the neonatal management of symptomatic CPAM is clear and includes prompt surgery, controversies remain for asymptomatic CPAM due to risk of infections and malignancies. What is new: • Increased rate of infection over time renders the surgery more difficult after months or years of evolution and pushes for recommendation of early elective surgery. • New molecular or pathological pathways may help in the distinction of type 4 CPAM from type I pleuropulmonary blastoma.

A novel in vitro model to study alveologenesis

Many pediatric pulmonary diseases are associated with significant morbidity and mortality due to impairment of alveolar development. The lack of an appropriate in vitro model system limits the identification of therapies aimed at improving alveolarization. Herein, we characterize an ex vivo lung culture model that facilitates investigation of signaling pathways that influence alveolar septation. Postnatal Day 4 (P4) mouse pup lungs were inflated with 0.4% agarose, sliced, and cultured within a collagen matrix in medium that was optimized to support cell proliferation and promote septation. Lung slices were grown with and without 1D11, an active transforming growth factor-β-neutralizing antibody. After 4 days, the lung sections (designated P4 + 4) and noncultured lung sections were examined using quantitative morphometry to assess alveolar septation and immunohistochemistry to evaluate cell proliferation and differentiation. We observed that the P4 + 4 lung sections exhibited ex vivo alveolarization, as evidenced by an increase in septal density, thinning of septal walls, and a decrease in mean linear intercept comparable to P8, age-matched, uncultured lungs. Moreover, immunostaining showed ongoing cell proliferation and differentiation in cultured lungs that were similar to P8 controls. Cultured lungs exposed to 1D11 had a distinct phenotype of decreased septal density when compared with untreated P4 + 4 lungs, indicating the utility of investigating signaling in these lung slices. These results indicate that this novel lung culture system is optimized to permit the investigation of pathways involved in septation, and potentially the identification of therapeutic targets that enhance alveolarization.

[Congenital cystic adenomatoid malformations of the lung: diagnosis, treatment, pathophysiological hypothesis]

Congenital cystic adenomatoid malformations (CCAM) of the lung are the most frequent congenital lung malformations. Their diagnosis is based on histological features. CCAM consist of bronchopulmonary cystic lesions which are classified according to the presence and cysts size. Type I CCAM are composed of large cysts (>2 cm) lined by a columnar pseudostratified epithelium. Type II CCAM contain multiple small cystic lesions (<1 cm) lined by a flattened cuboidal epithelium. Type III CCAM are more solid and contain immature structures resembling the pseudoglandular stage of lung development. Ultrasonography (US) allows early detection during the second trimester of pregnancy as cystic, and/or hyperechoic fetal lung lesions. Although most CCAM remain asymptomatic, CCAM can cause polyhydramnios or fetal hydrops, respiratory distress at birth, infections and pneumothoraces during infancy, and may give rise to malignancies. Serial US allow detection of complications, and planification of delivery. Complicated forms require an urgent treatment. In fetuses with a macrocystic life-threatening lesion, a thoraco-amniotic shunt can be placed. Microcystic compressive forms may respond to prenatal steroids. Post-natal symptomatic lesions require early surgery. The treatment of asymptomatic forms remains controversial. Some recommend a non-operative approach with a long-term clinical and radiological following, whereas other favour a preventive surgical excision. The origin of CCAM remains unknown. Recent advances suggest a transient and focal abnormality in lung development which may result from an airway obstruction. This article reviews the diagnosis, treatment, and pathophysiology of CCAM.

[Congenital lung malformations: natural history and pathophysiological mechanisms]

INTRODUCTION

Congenital lung lesions comprise a broad spectrum of various malformations including congenital cystic adenomatoid malformation (CCAM), bronchopulmonary sequestration (BPS), congenital lobar emphysema, bronchial atresia and bronchogenic cyst. This review aims at the description of their natural history, and of the underlying pathophysiological mechanisms.

STATE OF THE ART

Congenital lung lesions are frequently diagnosed antenatally and many remain asymptomatic after birth. In the absence of antenatal identification, they are usually revealed by the occurrence of infection. In some cases, spontaneous resolution of the malformation can occur. Different pathogenic hypotheses are discussed for the origin of these abnormalities, and common processes appear likely to all of these malformations. Factors involved in the process of branching seem to play a particularly important role.

PERSPECTIVES

Prospective follow-up of operated and unoperated children would complete our knowledge about the natural history of these lesions. The contribution of experimental models has led to advances in the understanding of pathogenic mechanisms. Further studies are needed to identify the factors initiating the malformative process.

Possible role of WT1 in a human fetus with evolving bronchial atresia, pulmonary malformation and renal agenesis

The association of peripheral bronchial atresia and congenital pulmonary airway malformation (CPAM) has recently been recognised, but the pathology of the lesions evolving together has not been described. We present autopsy findings in a 20 week fetus showing areas of peripheral bronchial destruction and airway malformation consistent with developing CPAM in the right lung supporting a causal relationship between these lesions. This fetus also had congenital heart defect, bilateral renal agenesis and syndactyly. We identified another fetus from our autopsy files, with bilateral renal agenesis, similar right sided pulmonary malformation and cardiac defects. Similar bilateral renal agenesis and defects of the heart and lungs are found in wt1(-/-) mice and we have investigated the expression of WT1 in these fetuses. We hypothesise that the cardiac, liver, renal and possibly lung lesions in these two cases may arise due to mesenchymal defects consequent to WT1 misexpression and discuss evidence for this from the scientific literature. We used immunoperoxidase stains to analyse WT1 expression in autopsy hepatic tissue in both fetuses. We also investigated the expression of α-smooth muscle actin (α-SMA), a marker of activated hepatic stellate cells/myofibroblasts, and desmin in hepatic mesenchyme and compare these findings with control fetuses, without congenital malformations. We found reduced WT1 expression in hepatic mesothelium in both fetuses with malformations. There was also increased expression of α-SMA in liver perisinusoidal cells, as seen in the wt1(-/-) mouse model. We therefore propose that abnormality of WT1 signalling may be an underlying factor, as WT1 is expressed in coelomic lining cells from which mesenchyme is derived in many organs.

Factors associated with partial and complete regression of fetal lung lesions

OBJECTIVE

A decrease in the volume of congenital pulmonary malformations (CPM) can be observed on prenatal ultrasonography, but the underlying mechanism for this phenomenon is unknown. Our objective was to identify factors associated with the prenatal reduction in size of cystic and/or hyperechoic lung lesions.

METHODS

This was a retrospective study of cases with a prenatal diagnosis of hyperechoic and/or cystic lung lesion. The extent of reduction in lesion size was calculated from ultrasound measurements. Clinical, ultrasound, radiological and histological data were tested for their relationship with prenatal CPM reduction.

RESULTS

In a 4-year period, 36 patients were referred with a cystic and/or hyperechoic fetal lung lesion diagnosed at a mean gestational age of 23.4 weeks. The lesions were cystic in 16 cases (44%), hyperechoic in 12 (33%) and both in eight (22%). The malformation was no longer visible before birth (apparent disappearance) in nine cases (25%), shrank by 18-90% in 15 (42%) and did not reduce in 12 (33%). Findings on postnatal computed tomography were always abnormal. Isolated hyperechoic lesions were significantly more likely to shrink in utero. The mean reductions were 79%, 35% and 19%, for isolated hyperechoic, cystic and mixed lesions, respectively (P=0.001). Only 8% of hyperechoic lesions demonstrated no volume reduction, as compared to 50% and 42% of cystic and mixed lesions, respectively (P=0.03). Greater gestational age at birth was also associated with a decrease in the incidence of malformations (P=0.02). In cases that underwent surgery, hyperechoic lesions were linked to a variety of pathological diagnoses, whereas cystic lesions were all described histologically as congenital cystic adenomatoid malformations.

CONCLUSIONS

Prenatal size reduction of fetal lung malformations is associated with isolated hyperechogenicity and greater gestational age at birth. This might result from the resumption of normal lung development after local disruption of lung growth.

Management of fetal lung lesions

Prenatal diagnosis provides insight into the in utero evolution of fetal thoracic lesions such as congenital cystic adenomatoid malformation (CCAM), bronchopulmonary sequestration (BPS), congenital lobar emphysema, and mediastinal teratoma. Serial sonographic study of fetuses with thoracic lesions has helped define the natural history of these lesions, determine the pathophysiologic features that affect clinical outcome, and formulate management based on prognosis.

Congenital cystic lung disease: contemporary antenatal and postnatal management

Congenital cystic lung disease comprises a broad spectrum of rare but clinically significant developmental abnormalities, including congenital pulmonary adenomatoid malformations, bronchopulmonary sequestrations, bronchogenic cysts, and congenital lobar emphysema that result from perturbations in lung and airway embryogenesis. As congenital lung lesions are now more commonly recognized antenatally, mothers require accurate prenatal counseling and appropriate perinatal management. In light of long-term complications of infection and malignancy, there is growing consensus that infants with asymptomatic lesions should undergo elective excision of congenital pulmonary adenomatoid malformation (CPAM) or bronchopulmonary sequestration (BPS). This review will focus on advancements and current practice in the diagnosis and management of CPAM and BPS, identifying aspects of the literature that are confusing or controversial. Although our knowledge and pre- and postnatal management of lung lesions will continue to evolve and improve, there is a compelling need for a unified clinical and pathological classification system that creates a common platform for discussion, clinical management, and research.

Laser microdissection allows detection of abnormal gene expression in cystic adenomatoid malformation of the lung

BACKGROUND/PURPOSE

Congenital cystic adenomatoid malformation (CCAM) of the lung may result from a localized aberrant epithelial-mesenchymal interaction during lung development. We used laser microdissection (LMD) to isolate the epithelium and mesenchyme of CCAM, and studied candidate gene expression in these pure cell populations.

METHODS

Congenital cystic adenomatoid malformation tissue was obtained from fetal (n = 5) and postnatal (n = 5) surgical specimens. Normal fetal lung (n = 10) was obtained from abortus material, and normal postnatal lung (n = 5) was identified from surgical specimens. Whole tissue was analyzed using immunohistochemistry and reverse transcriptase polymerase chain reaction (RT-PCR). Using LMD, columnar bronchiolar type epithelium and underlying mesenchyme were isolated. Multiplex nested RT-PCR was then used to detect message levels of candidate genes.

RESULTS

Reverse transcriptase polymerase chain reaction performed on LMD-isolated tissue, but not whole tissue homogenate, revealed differences between CCAM and normal lung. In this report, we focus on the fibroblast growth factor (FGF) family. By RT-PCR, there was 4-fold more epithelial expression of FGF9 in fetal CCAM vs normal fetal lung (P < .07). This was qualitatively confirmed by immunohistochemistry. We also detected decreased FGF7 expression in CCAM mesenchyme (P < .05) but no significant differences in FGF10 or FGFR2.

CONCLUSIONS

LMD may be used to overcome the limitations of tissue heterogeneity in the study of CCAM. Abnormal growth factor expression may play a role in the etiology of this lesion.

Antenatal diagnosis and management of congenital cystic adenomatoid malformation

One of the most enigmatic pulmonary lesions encountered in the prenatal period is the congenital cystic adenomatoid malformation (CCAM). This review presence current thinking on pathogenesis, prenatal assessment, fetal intervention, and management for this pulmonary malformation. Careful delivery planning by utilizing a multidisciplinary approach will optimize neonatal outcomes.