Answer

We present a case of Congenital cystic adenomatoid malformation (CCAM)

Discussion

Congenital cystic adenomatoid malformations (CCAM) of lung are rare congenital cystic lung lesions that arise from excessive proliferation of tubular bronchial structures [1]. It is a rare lesion with incidence of 1 in 25,000 to 1 in 35,000 pregnancies and represents 25% of congenital lung malformations and 95% of congenital lung lesions [2].  It was classified into 3 subtypes in 1977,  and expanded into five types and renamed as congenital pulmonary airway malformation (CPAM) by Stocker in 2002 [3, 4] Eighty percent of the lesions are recognized in neonatal period; however, there are reports even in adult population[5].  It is usually unilateral and restricted to a single lobe [6]. In, up to 10% of the cases additional extra-pulmonary abnormalities can be found, such as renal, central nervous, gastrointestinal, and cardiac defects [7].

CCAM is a rare developmental, non-hereditary, hamartomatous abnormality of lung with unknown etiology. This condition was first described by Chi’n Tang in 1949[8]. Males and females are equally affected. Based on the anatomical changes, development of human lung is subdivided into embryonal (3-7 weeks), pseudo glandular (7-17 weeks), canalicular (17-29 weeks), saccular (24-36 weeks), and alveolar (36 weeks to maturity). CCAM develops during the pseudo glandular and saccular period (7-35 weeks)[1].

Stocker et al., in 1977,[ 3] subdivided CCAM into three subtypes. Type I lesion constitute 50-70% and is composed of single or multiple large cysts (> 2 cm) lined by flattened, cuboidal cells frequently producing mediastinal herniation. The walls of the cysts contain prominent smooth muscle and elastic tissue. Occasionally mucus producing cells are seen and presence of cartilage is extremely rare. Mucin production is unique to type I lesion (as observed in our case 2). Type II lesion constitute 15-30% and are composed of multiple small cysts (< 2 cm), lined by ciliated cuboidal to columnar epithelium, structure resembling that of respiratory bronchioles, and distended alveoli are present between the epithelium lined cyst. Mucus cells and cartilage are not seen. This type is usually associated with other systemic anomalies. Type III lesion constitutes 5-10% and are usually large bulky non-cystic lesions producing mediastinal shift. Bronchial-like structures are lined by ciliated cuboidal epithelium and separated by masses of alveolus-sized structures by non-ciliated cuboidal epithelium [9]. Systemic anomalies reported in Type II lesions include; renal anomalies (B/L renal agenesis, abnormalities of ureter, bladder, and urethra), abdominal wall defects, central nervous system defects (hydrocephalus), spinal deformities, gastrointestinal defects (diaphragmatic hernia, jejuna atersia, tracheoesophageal fistula, and imforforate anus), cardiac anomalies (ventriculoseptal defects, tetralogy of fallot, and truncus arteriosis), sirenomelia, and anomalies of reproductive tract.

The diagnostic sonographic ultrasonographic feature of CCAM is, multicystic lesions at the lung field and common differential diagnosis includes diaphragmatic hernia, bronchogenic cyst, cystic fibrosis, congenital lobar emphysema, and pulmonary sequestration. CCAM will have connections to tracheobronchial tree and derives its blood supply from pulmonary circulation. Meanwhile, pulmonary sequestration contains immature lung tissue without connection to tracheobronchial tree and derives its blood supply from aberrant systemic blood vessel. Previously, for patients with CCAM fetuses the termination of the pregnancy were advised due to presumed poor prognosis, but recent studies changed the tactic for those cases. There are reports of even disappearance of lesion on serial USG examination [10].

For the lung masses, the intrauterine prognosis of the fetus is determined by fetal lung mass size (a single measurement of lung mass at the maximum diameter) or by the CCAM volume ratio (CVR). CCAM volume is calculated by using a formula for prolate ellipse, with measurements of lung mass in three perpendicular planes. The CVR is calculated by dividing the CCAM volume by head circumference (HC, measured in centimeter). Thus CVR = (L × B × W × 0.52/HC) [11]. It wase revealed that the size of the lung mass or CVR correlated strongly with the fetal outcome. The observed threshold values in their study were 5.2 cm for mass size and 2 for CVR. There was 100% survival of fetuses with mass values less than 5.2 cm and CVR < 2. In the fetuses with lung mass size more than 5.2 cm or CVR more than 2 were associated with marked mediastinal deviation, hydrops, ascites, and heart failure. Also the fetal echocardiography could be helpful in management of these fetuses. If there are no signs of heart failure, then the fetuses will be benefited by maternal steroid therapy and serial thoracocentesis. Those fetuses with impending cardiac failure needed open fetal surgeries[11].

The commonest presentation of CCAM in postnatal life is progressive respiratory distress including tachypnea, grunting, retraction, and cyanosis; and in adults it usually presents as repeated chest infections. Chest X-ray, computed tomography (CT), and magnetic resonance imaging (MRI) are helpful in diagnosis.

The main complication of CCAM in neonatal period is compression of the mediastinal structure producing cardiovascular compromise. In adult patient, CCAM could suffer from pneumonia, abscess formation, fungal infections, spontaneous pneumothorax, hemoptysis, air embolism, intralobar sequestration, and development of bronchogenic carcinoma. Serial antenatal sonographic evaluation, good obstetric care, and delivery at a tertiary care center are preferred plan of treatment for antenataly detected cases. Postnatal and in adults patients, lobectomy is the treatment of choice for symptomatic cases.

Prognosis also depends on Stocker type, type I lesions carry overall good prognosis. In type II lesion, it is the associated anomalies that determine the prognosis. Type III lesions carry bad prognosis as they are usually large and presents with cardiovascular compromise. Overall bilateral involvement, associated with hydrops and associated congenital anomalies carry poor prognosis[12].

References

1. Sood M, Sharma S. Congenital cystic adenomatoid malformation of lung-A case report Currt Pediatr Res. 2011;15:61–3.
2. Laberge JM, Flageole H, Pugash D, et al. Outcome of the prenatally diagnosed congenital cystic adenomatoid lung malformation: a Canadian experience. Fetal Diagn Ther 2001; 6:178–186.
3. Stocker JT, Madewell JE, Drake RM. Congenital cystic adenomatoid malformation of the lung. Classification and morphologic spectrum Hum Pathol. 1977;8:155–71.
4. Stocker JT. Congenital pulmonary airway malformation: A new name and an expanded classification of congenital cystic adenomatoid malformation of the lung Histopathol. 2002;41:424–31.
5. Feng A, Cai H, Sun Q, Zhang Y, Chen L, Meng F. Congenital cystic adenomatoid malformation of lung in adults: 2 rare cases report and review of the literature Diagn Pathol. 2012;7:37.
6. Davenport M, Warne SA, Cacciaguerra S, et al. Current outcome of antenally diagnosed cystic lung disease. J Pediatr Surg 2004; 39:549–556.
7. Stocker JT. Congenital and developmental diseases. In: Dail DH, Hammer SP, editors. Pulmonary pathology, New York: Springer. 1994; 2nd ed:174-180.8.Khan NU, Jones MT, Greaves M. Case report: Congenital cystic adenomatoid malformation of an entire lung in a 33-year-old man: A case report and review of the literature Br J Radiol. 2008;81:e276–89. Sfakianaki AK, Copel JA. Congenital cystic lesions of the lung: Congenital cystic adenomatoid malformation and bronchopulmonary sequestration Rev Obstet Gynecol. 2012;5:85–93.10. Hsu YR, Lee SY. Prenatal diagnosis of congenital cystic adenomatoid malformation Chang Gung Med J. 2004;27:61–5.
11. Cass DL, Olutoye OO, Cassady CI, Moise KJ, Johnson A, Papanna R, et al Prenatal diagnosis and outcome of fetal lung masses J Pediatr Surg. 2011;46: 292–8.
12. Annam V, Korishetty SI, Yelikar BR, Hippargi SB, Shivalingappa DB. Bilateral congenital cystic adenomatoid malformation, stocker type III with associated findings and review of literature Indian J Pathol Microbiol. 2010;53:331–3.

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