Congenital pulmonary airway malformation of a congenital lung disease with a potential hybrid lesion: A case report

Abstract

BACKGROUND

Congenital pulmonary airway malformation (CPAM), formerly known as congenital cystic adenomatoid malformation is a congenital lung lesion associated with cystic and non-cystic lung malformations that arise from abnormal branching during the embryological development of lung. The diagnosis is based on a combination of gross and microscopic features. Modified Stocker classification is used to subtype these malformations. These anomalies are usually benign, with few types with the risk of undergoing malignant transformation.

CASE SUMMARY

A 5 years 9 months old female child complained of fever, on and off since 1 month. There were no additional complaints. No associated past history. On performing investigations, computed tomography chest showed an incidental multicystic lesion in right lower lobe situated medially and posteriorly suggestive of an intralobar sequestrum along with an airway malformation with collection of infected serous fluid within the cystic spaces.

CONCLUSION

CPAM type-2 with a possible adjacent acquired intralobar sequestrum can be a potential hybrid lesion.

Key Words: Cystic pulmonary airway malformation; Sequestration; Congenital; Hybrid; Case report

Core Tip: Cystic pulmonary airway malformation is a congenital lung lesion associated with abnormal branching during the embryological development of lung leading to cystic and non-cystic lung malformations. The diagnosis of this condition is based on a combination of gross and microscopic features. Appropriate classification into its type of lesion is of an utmost necessity. The classification of lesion predicts the prognosis, possibility of malignancy and other congenital anomalies. Early detection of the anomaly can also help in prevention and progression of malignancy.

INTRODUCTION

Congenital pulmonary airway malformations (CPAMs) are among the common congenital lung lesions. They are a spectrum of cystic or non-cystic malformations of lung associated with abnormal branching or atresia during embryologic development[1]. The diagnosis is based on a combination of gross and microscopic features[2]. The prevalence of CPAMs is about 1 in 11000 births[3,4]. These malformations were identified incidentally as part of a postnatal evaluation for other anomalies in earlier times. Few cases were identified after symptomatic presentation such as hemodynamic or respiratory compromise in newborns or as an infection in children.

In the past few years, with the advent of universal prenatal ultrasound examination of the fetus, many new information about these congenital malformations has been gained[1,3]. A careful correlation of radiological evidence postnatally is the key to pick up such a lesion on chest radiograph or computed tomography (CT) radiograph which helps in early surgical intervention in terms of location, size, number and size of cysts and its content.

Treatment protocol in these patients involve early surgery, which is well tolerated with less morbidity and decreased risk of recurrent infections and malignancy[3]. Pathologic analysis of cystic lung disease in children has important role in placing a disease into one of the following several different categories which includes CPAMs, intra-lobar sequestration (ILS) and extra-lobar sequestration (ELS), bronchial atresia (BA), and bronchial obliteration. Unlike ILS, ELS, and BA, the diagnosis of CPAMs is based on macroscopic and microscopic criteria rather than on anatomic relationships of bronchial tree, blood vessels, and pleura[5].

The subtypes of CPAM have been assigned by the Stocker classification (type 0-4)[2] (Table 1). Subtypes are denoted on the basis of the disease originating from the different parts of the bronchial tree. This classification helps in subsequent differentiation in clinical features, histopathology and the risk of malignancy and prognosis. CPAM type 1 being the most common type includes 70% of all CPAMs. CPAM type 2 is the second most frequent type often associated with other types of anomalies (renal agenesis, cardiovascular defects, diaphragmatic hernia, esophageal atresia, skeletal defects). Type 4 CPAMs are very rare[2,3].

Table 1 Features of congenital pulmonary airway malformation as per Stocker classification.

Types	Site of origin	Morphological features	Prognosis
Type 0	Trachea/bronchi	Bronchial type airways with cartilage, smooth muscles, and glands separated by mesenchyme	Incompatible with life
Type 1	Bronchi	Multiloculated cysts, lined by pseudo-stratified columnar epithelium and located within one lobe	Excellent prognosis following resection. Rarely undergoes malignant transformation
Type 2	Bronchiolar region	Multiple small cysts with no mass effect	Good prognosis with no malignant potential
Type 3	Bronchiolar regions	Involves and expands an entire lobe compressing the other lobes, maybe solid or cystic. Absent pulmonary arteries within the lesion	Good prognosis with no malignant potential
Type 4	Acinar structures of the lung	Peripheral thin-walled multiloculated cysts, lined by alveolar type 1 or type 2 cells	Strong association with type 1 pleuro-pulmonary blastomas[2,3]

CASE PRESENTATION

Chief complaints

A 5 years 9 months old female child complained of fever.

History of present illness

She complained of fever on and off for a month. There were no additional complaints.

History of past illness

No associated past history.

Personal and family history

Not contributory.

Physical examination

No significant findings on clinical examination except fever.

Laboratory examinations

Laboratory examinations mainly showed leukocytosis on complete blood count. No microbiology studies like culture studies were performed in relation to the lesion as patient had taken broad spectrum antibiotics in view of on and off fever.

Imaging examinations

CT chest showed an incidental multicystic lesion in right lower lobe situated medially and posteriorly suggestive of an intralobar sequestrum along with an airway malformation with collection of infected serous fluid within the cystic spaces. Figure 1 shows CT radiographic images showing the lesion. For surgical intervention, Lobectomy of right lower lobe was performed and sent for histopathological examination. Patient tolerated the surgery well.

Figure 1 Computed tomography chest images of the lesion showing a multicystic lesion in right lower lobe situated medially and posteriorly suggestive of an intralobar sequestrum with a congenital cystic malformation. A-C: Lesion can be seen with arrowheads in coronal view (A) and in axial views (B and C).

FINAL DIAGNOSIS

Infected cystic pulmonary malformation.

TREATMENT

Patient had taken antibiotic treatment for on and off fever followed by lobectomy of right lower lobe (Figure 2).

Figure 2 Specimen of right lower lobe of lung. A: Externally the surface was irregular; B: Cut surface showed multiple cysts filled with pus and mucoid material; C and D: Histopathological features: Multiple blood vessels are seen with few appearing thick walled along with dilated cysts lined by ciliated columnar epithelium (4× magnification) (C) containing pools of mucin (mucostasis) (10× magnification), acute inflammation and necrosis (D); E: Dilated alveoli showed collection of foamy macrophages (10× magnification).

OUTCOME AND FOLLOW-UP

Patient lost to follow up.

DISCUSSION

The above-mentioned case was a 5 years 9 months female child with a complaint of fever since one month with incidental detection of right lower lobe airway malformation on CT chest. In this case CPAM coexisted with intralobar sequestration. Radiological findings played a key role in detection and guided for surgical intervention. The congenital lesion in this case was not picked up on anomaly scan which later presented after involvement of the lesion by a superadded infection.

Histopathological examination was suggestive of a CPAM- type 2. This type is the second most common type after type 1 malformation not associated with other types of anomalies. The prognosis of this patient is good as there is no risk of malignancy. A close follow up is necessary to ensure the success of the surgical management.

Stocker et al[2] suggested that intralobar sequestration is acquired even though CPAM in congenital. They have suggested that the pleural ligament arteries supplying the sequestrum are a part of normal anatomical structure. The hypertrophy of the enlarged arteries within the lesion occurs due to the response to inflammation[2]. This implies that the lesion of CPAM type 2 in this study coexisting with an intralobar sequestration can be due to the normal anatomical variant in vasculature and changes associated with inflammation due to the superadded infection putting it in the discussion of a hybrid lesion.

Pogoriler et al[3] discussed about the case series on a spectrum of congenital cystic pulmonary lesions which included intralobar sequestration, extralobar sequestration, CPAM bronchial atresia and bronchogenic cysts. It also described around 184 prenatally diagnosed cases of cystic lesions including CPAM. Most of the CPAM type 1 lesions would be symptomatic, detected postnatally and undergo resection. CPAM type 2 cases may remain undetected. It also suggests that for a lesion with features of both CPAM type 2 and sequestration, the term “Hybrid lesion” can be coined due to their overlapping features which are the findings in this case study as well.

Nelson et al[4] discussed a case of CPAM type 1 with the focus of mucinous cell clusters mimicking adult mucinous adenocarcinoma of lung. The patient underwent a complete surgical resection of the lesion. The risk assessment of malignant progression was not possible to establish following the complete resection of the specimen. For a year after surgery, patients were followed up with chest X-rays to look for recurrence. None of the CPAM cases came back with a reported mucinous adenocarcinoma of lung. In this case our patient was lost to follow up[4].

Imai and Mark[5] suggested that the extralobar sequestration coexisting with congenital cystic adenomatoid malformation (CCAM) has been described in many cases where some cases showed connection of esophagus or stomach presenting as fibrous bands or the lesions of the lumen. It also suggests that in utero CCAM is congenital as per the natural history but CCAM detected postnatally on microscopy could be a development of the lesion after the child’s birth[5].

CONCLUSION

CPAM is a congenital lung lesion associated with abnormal branching during the embryological development of lung leading to cystic and non-cystic lung malformations[1]. Early detection includes prenatal anomaly ultrasound scans and postnatally with CT chest radiographs. In this case, recurrent infections and incidental detection of lesion of CT chest helped in deciding the course of treatment. The diagnosis of this condition in this case is based on a combination of gross and microscopic features. Appropriate classification into its type of lesion is of an utmost necessity[2,3]. The classification of lesion predicts the prognosis, possibility of malignancy and other congenital anomalies[4,5]. Closest resembling entity includes an intralobar sequestration which can be acquired as per few studies[2]. The overlapping features of intralobar sequestrum and CPAM type 2 are seen in this study. The features of intralobar sequestrum with adjacent maldeveloped lung is known as a “hybrid lesion” which can be a possibility in the above case report[3].