Epidemiology

 25% of all congenital lung lesions
 4-26% of cases can be associated with other congenital abnormalities.
 estimated incidence: 1 case per 25,000-35,000 pregnancies.

Subtypes

 CPAM type O - CCAM type O (acinar dysplasia)
 CPAM type 1 - CCAM type 1 (bronchial/bronchiolar)
 CPAM type 2 - CCAM type 2 (bronchiolar)
 CPAM type 3 - CCAM type 3 (bronchiolar/alveolar duct)
 CPAM type 4 - CCAM type 4 (peripheral)
 CPAM type 5 - CCAM type 5

CCAM type 0 (congenital acinar dysplasia, congenital acinar aplasia) (1-3%) (neonates, other malformations, poor prognosis)

 solid appearance
 small and firm lungs
 bronchial-type airways with cartilage, smooth muscle and glands separated by abundant mesenchymal tissue

CCAM type 1 (60-70%) (bronchial) (neonates and infants, resectable, good prognosis, possible carcinomatous change)

 1 or more large cysts measuring 2-10 cm in diameter. Larger cysts are often accompanied by smaller cysts, and their walls contain muscle, elastic, or fibrous tissue.
 cartilaginous plates (12%) (#12883247#)
 Cysts are frequently lined by pseudostratified columnar epithelial cells often interspersed with rows of mucous cells
 focal mucous cell hyperplasia (12 to 25% of type 1 CCAM)
 microscopic foci of bronchioloalveolar carcinoma (1 to 31% of type 1 CCAM) (#12883247#)

CCAM type 2 (10-15%) (bronchial/bronchiolar) (neonates, other malformation, poor prognosis)

 sponge-like appearance
 multiple small cysts (0.5 to 2 cm)
 small relatively uniform cysts resembling bronchioles separated by normal alveoli
 cysts are lined by cuboid-to-columnar epithelium and have a thin fibromuscular wall.
 solid pale tumor-like tissue
 striated muscle in 5%

CCAM type 3 (5%) (bronchiolar) (neonates, poor prognosis)

 solid appearance
 excess of bronchiolar structure separated by small air spaces, with cuboidal lining, resembling late fetal lung
 grossly a solid mass without obvious cyst formation
 microscopic adenomatoid cysts

CCAM type 4 (28%) (peripheral) (neonates and infants, good prognosis)

 large cysts (up to 10 cm)
 cysts lined by a flattened epithelium (type 1 and 2 pneumocytes) resting on loose mesenchymal tissue
 focal stromal hypercellularity (50%) (#12883247#)
 focal immature cartilage (#12883247#)
 associated pleuropulmonary blastoma (bilateral type 4 CCAM with stromal cellularity) (14%) (#12883247#)

Associations

 pulmonary malformations

• extralobar sequestration (CCAM type 2 and CCAM type 3) with systemic arterial supply
• controlateral extralobar pulmonary sequestration (#15300558#)
• bronchial atresia (#7298053#)
• polyalveolar lobe

 epithelial hyperplasias

• atypical goblet cell hyperplasia
• nonmucinous atypical adenomatous hyperplasia
• focal mucous cell hyperplasia (25% of type 1 CCAM)

 renal malformations

• ipsilateral multicystic renal dysplasia (#15630540#)
• contralateral renal agenesis (#15630540#)

 ovarian germ cell hypoplasia (#15630540#)

 malignant tumors

• pleuropulmonary blastoma (bilateral type 4 CCAM with stromal cellularity) (14%) (#12883247#)
• rhabdomyosarcoma (#16007610#, #11431779#, #9314270#)
• malignant mesenchyma
• bronchioloalveolar carcinoma (31% of type 1 CCAM) (#12883247#, #9475333#)
• atypical goblet cell hyperplasia ((#15138930#)

 chromosomal anomalies

• trisomy 13 (#12673637#)
• trisomy 18 (#11173951#)
• chromosme 18 rearrangement (partial deletion of 18p and partial duplication of 18q) (#11173951#)

 miscellaneous

• aneurysm of the vein of Galen (#15022074#)

Diferential diagnosis

 stromal cellularity in a type 4 CCAM should raise the possibility of blastomatous transformation.

See also: congenital pulmonary cysts

References

 Wilson RD, Hedrick HL, Liechty KW, Flake AW, Johnson MP, Bebbington M, Adzick NS. Cystic adenomatoid malformation of the lung: Review of genetics, prenatal diagnosis, and in utero treatment. Am J Med Genet A. 2006 Jan 15;140(2):151-5. PMID: #16353256#

 Pai S, Eng HL, Lee SY, Hsiao CC, Huang WT, Huang SC. Rhabdomyosarcoma arising within congenital cystic adenomatoid malformation. Pediatr Blood Cancer. 2005 Nov;45(6):841-5. PMID: #16007610#

 MacSweeney F, Papagiannopoulos K, Goldstraw P, Sheppard MN, Corrin B, Nicholson AG. An assessment of the expanded classification of congenital cystic adenomatoid malformations and their relationship to malignant transformation. Am J Surg Pathol. 2003 Aug;27(8):1139-46. PMID: #12883247#

 Stocker JT, Madewell JE, Drake RM. Congenital cystic adenomatoid malformation of the lung. Classification and morphologic spectrum. Hum Pathol. 1977 Mar;8(2):155-71. PMID: #856714#

 Cha I, Adzick NS, Harrison MR, Finkbeiner WE. Fetal congenital cystic adenomatoid malformations of the lung: a clinicopathologic study of eleven cases. Am J Surg Pathol. 1997 May;21(5):537-44. PMID: #9158677#

 Cangiarella J, Greco MA, Askin F, et al. Congenital cystic adenomatoid malformation of the lung: insights into the pathogenesis utilizing quantitative analysis of vascular marker CD34 (QBEND-10) and cell proliferation marker MIB-1. Mod Pathol 1995; 8:913-8.