Perpetual dilemma: Pleural or parenchymal/congenital or acquired solitary cystic lesion with fluid level.

Congenital cystic adenomatoid malformations (CCAMs) are rare congenital, nonhereditary developmental anomalies of the lung with unknown etiology. CCAM is predominantly a disorder of infancy with the majority of the cases being diagnosed within the first 2 years of life. When CCAM presents in adults, it represents a diagnostic dilemma and requires careful evaluation. We here report a case of large solitary congenital pulmonary cystic adenomatoid malformation with infection and hemorrhage, which was diagnosed as encysted hydropneumothorax on computerized tomography scans but turned out to be infected pulmonary cystic adenomatoid malformation after surgical excision.

INTRODUCTION

Intrathoracic cysts need to be accurately localized to pulmonary or pleural origin on the basis of clinical presentation and laboratory tests before considering further differential diagnosis. This is truly intriguing as large parenchymal cysts or emphysematous bullae have been reported to be confused with hydropneumothorax with intercostal drains being put leading to complications.[1] However, if localized to lung, such large cyst in adults is likely to be infective in origin with history of recurrent lower respiratory tract infections.[2] Congenital parenchymal cysts are mostly asymptomatic in adults and may be picked up as an incidental finding.[3] Bronchogenic cysts, cystic adenomatoid malformation, and sequestration are congenital conditions rarely associated with large isolated cystic lesion in the lungs. We report a case of large solitary lesion with air-fluid level, which was diagnosed as encysted hydropneumothorax in oblique fissure on contrast-enhanced computerized tomography (CECT) of thorax but turned out to be infected pulmonary cystic adenomatoid malformation after surgical excision.

CASE REPORT

A 45-year-old male, defense personnel by occupation, smoker with a history of significant alcohol intake, presented with fever with chills, cough with expectoration, and right-sided pleuritic chest pain for 1 month associated with significant weight loss (5 kg). He consulted a local physician and was started on antitubercular treatment (ATT) on radiological basis. There was no symptomatic improvement, and he was admitted to our center for further management. On detailed history, the patient gave a history of taking complete ATT for similar complaints and right-sided effusion 10 years and again 2 years ago. On examination, he was afebrile, with stable vitals and room air saturation of 96%. There were no abnormal findings on general or systemic examination except diminished breath sounds on the right side of the chest posteriorly. Laboratory investigations revealed hemoglobin – 11.3 gm%, total leukocyte count – 7100/cu mm with normal differential count (polymorphs 67% and lymphocytes 29%), platelets – 3.70 L/cu mm, and normal liver and kidney function tests. His chest skiagrams showed air-fluid level on the right side in a large solitary lesion suggestive of encysted hydropneumothorax or infected giant bulla [Figure 1a and b]. Sputum for acid-fast bacilli (AFB) smear was negative and pyogenic culture showed no growth. Hydatid serology and serum galactomannan were negative. CECT of the thorax showed a large smooth-walled cystic lesion with air-fluid level below the oblique fissure with upper margin of the cyst abutting the fissure and infiltrating the right lower lobe (RLL) [Figure 1c–f]. Aortography revealed no independent arterial supply to the cyst. These findings raised the possibility of encysted hydropneumothorax in oblique fissure. The patient underwent fiberoptic bronchoscopy, which revealed thick purulent secretions in RLL, and bronchoalveolar lavage was negative for AFB smear, fungal smear, and pyogenic culture. Patient's CECT of the thorax done 2 years back was retrieved which showed similar findings with smaller size [Figure 2a–b (old CECT 2012) compared with c-d (new CECT)]. In view of persistent lesion not responding to treatment, he underwent video-assisted thoracoscopic surgery for removal of the lesion from RLL with surrounding lung and segmentectomy [Figure 3a and b]. Histopathology of specimen revealed intact cystic lesion with cyst wall lined with ciliated pseudostratified columnar epithelium (bronchiolar type) without cartilage and surrounding lung showing alveoli filled with proteinaceous periodic acid-Schiff-negative exudate and hemorrhage [Figure 3c–e] establishing diagnosis of congenital pulmonary cystic adenomatoid malformation with infection and hemorrhage. Postoperatively, the patient recovered well, was discharged on day five, and was doing well at 1-year follow-up.

Figure 1

(a and b) Chest X-ray posterior-anterior and right lateral view showing large cystic lesion in the right lung in lower lobe. (c-f) Computerized tomography images showing cystic lesion is limited by fissure with patchy consolidation in apical segment of right lower lobe with thickened oblique fissure, interpreted as encysted pyopneumothorax in right oblique fissure

Figure 2

Computerized tomography images of 2013 in upper panel (a and b) and 2015 in lower panel (c and d) where the cystic lesion seems to have expanded with surrounding consolidation of the right lower lobe in c and d

Figure 3

(a and b) Thoracotomy with gross specimen of removed cyst and segmentectomy. Histopathology of specimen (c-e) showed cyst wall lined by pseudostratified ciliated columnar epithelium with inflammation and hemorrhage in surrounding lung parenchyma in H and E stains

DISCUSSION

Congenital cystic adenomatoid malformation (CCAM) is a rare congenital disease first described by Chin and Tang[4] in 1949 due to hamartomatous overgrowth of bronchioles, with almost complete suppression of alveolar development. The incidence of CCAM has been estimated at 1:25,000–1:35,000 pregnancies in one study[5] while another reports a population prevalence of 9/100,000 total births.[6]

This entity is characterized by multiple solid cystic lesions which generally present as neonatal respiratory distress syndrome. There is no predilection for either side or lobe of the lung.[7] This condition is different from closely resembling rare congenital intrapulmonary bronchogenic cysts which are mostly mediastinal and airway centric in location.[8] Bronchogenic cysts contained normal tracheal tissue including mucus glands, elastic tissue, smooth muscle, and cartilage and lined by ciliated epithelium while CCAM is only lined by respiratory epithelium with absence of cartilage, muscle, and glands, hence requiring pathological examination of the cyst wall for diagnosis. Pulmonary sequestration also closely resembles CCAM but is supplied by independent vascular supply, which needs to be evaluated by aortography prior to surgical management in all such cystic lesions, or else catastrophic intraoperative bleeding can occur.[9]

Traditionally, CCAM can be classified into three types (stocker classification) [Table 1].[10]

Table 1

Stocker's classification of CCAM

Presentation in adults is rare being with mean age at the time of diagnosis being 30.3 years. Patients are usually asymptomatic in two-third cases and uncommonly present as recurrent lower respiratory tract infections of one lobe. It may also present as a mass lesion with variable amount of solid and cystic components and may communicate with the bronchial tree. Since neither all are cystic nor all are adenomatous, it is more appropriately now called as congenital pulmonary airway malformations (CPAMs).[11]

CPAM is frequently mistaken for congenital diaphragmatic hernia in newborns and sequestration or pulmonary bronchogenic cyst in adults. CT imaging reveals mostly cystic lesions of varying sizes and irregular shapes, filled with air, multifocal, and predominantly in lower lobes and has significant overlapping findings.[12] Rare “macrocystic type” is hard to distinguish from lung cyst as was in our case with air-fluid level. Differential diagnosis in adults with infection is difficult as distinction between congenital versus acquired etiology is distorted and includes abscess, tuberculosis, hydatidosis, or vasculitis.[11] This leads to considerable delay in final diagnosis which requires histopathology of the surgical specimen. Frequent mimic on imaging in adults is pyopneumothorax and has led to intercostal tube being put in cyst with fluid level. Spontaneous pneumothorax due to rupture of the cyst has been reported at the time of presentation causing clinical confusion. Hence, the emerging consensus is that imaging findings should simply be described, without attempting to make a pathological diagnosis on radiology.[13]

Besides infection other complications, for example, hemorrhage, enlargement with space occupying effect, and subsequent development of squamous or adenocarcinoma have been reported. Clinico-radiological changes prompt for early investigation to exclude malignancy in long-standing cysts and require surgical removal as noninvasive tests are unreliable.[14]

Our patient, on serial CT scans, showed an enlargement of the cyst with fluctuating fluid levels and was already complicated at the time of presentation. Enlargement of cyst was not seen in bronchogenic cysts, and the absence of anomalous systemic vascular supply was clues to the correct preoperative diagnosis of CCAM. However, superadded infection, juxta-fissural position, and previous history of pleural effusion tilted the diagnosis toward encysted hydropneumothorax although a high index of suspicion prevented mishap of putting an intercostal drain.

Management of CCAM of the lung is surgical resection, recommended to confirm the diagnosis and lessen the future risk of infection or malignant degeneration.[15] Prognosis after radical excision is excellent and hence recommends even in asymptomatic patients. Many surgeons and pathologists recommend lobectomy as it is safer and because demarcation between CCAM and normal parenchyma is impossible on grossing. Others recommend segmental resection but may lead to incomplete excision and residual pneumothorax.[16] In our patient, surgeon's choice to perform segmentectomy with complete removal of cyst was dictated by need to preserve lung functions as far as possible by job requirement of patient as well as his confidence in complete excision of cyst and surrounding abnormal lung tissue which was also confirmed by pathologist. There has not been a recurrence in 1-year follow-up of the patient till now.

CONCLUSION

We reported a case who presented as loculated pyopneumothorax on clinico-radiological grounds, treated with ATT twice; however, high index of suspicion not only led to correct diagnosis of CPAM but also prevented potentially catastrophic implantable cardioverter defibrillator placement, emphasizing need for better understanding of congenital lung diseases presenting in late adulthood where such diagnosis is generally not entertained on account of being late for such conditions.

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Conflicts of interest

There are no conflicts of interest.