Congenital Cystic Adenomatoid Malformation (CCAM)

Epidemiology and Etiology:

· hamartoma

Common sites:

·

Gross features:

· cystic (some)

· unilateral and confined to one lobe usually

·

Histologic features:

o Increase in structures resembling terminal bronchioles compared to normal lung

§ Ciliated epithelium (except type 4)

§ Cartilage is only rarely present

o Polypoid growths of cuboidal epithelium and increased underlying stromal elastica and smooth muscle often

o Think of different types as going proximal to distal from 0-4

o Type 0:

§ bronchial-like structures,

§ cartilage plates, and

§ loose vascularized mesenchyme

o Type 1 (>65%):

§ Up to 10cm cyst size

§ Ciliated, pseudostratified tall columnar epithelium

§ Mucous cells maybe present

§ Cartilage may be present

§ Skeletal muscle absent

o Type 2 (20-25%)

§ Up to 2.5cm cyst size

§ Ciliated, cuboidal or columnar epithelium

§ Absent mucous cells

§ Absent cartilage

§ Skeletal muscle maybe present (5-10%)

o Type 3 (8%)

§ Up to 1.5cm cyst size

§ Ciliated, cuboidal epithelial lining

§ Thinner muscular wall thickness of cyst

§ Absent mucous cells

§ Absent cartilage

§ Absent skeletal muscle

o Type 4 (2-4%)

§ 7.0cm max cyst size

§ Flattened, alveolar lining cells

§ Absent mucous cells

§ Absent cartilage usually

§ Absent skeletal muscle

Immunophenotype:

Marker:

Sensitivity:

Specificity:

Molecular features:

·

Other features:

· May predispose to recurrent infections if not resected

· Type 4 CCAM must be differentiated from type I PPB, but may be difficult or impossible

· Both present with pneumothorax

· Type 1 CCAM – associated risk of BAC

References:

· Travis WDM. Non-Neoplastic Disorders of the Lower Respiratory Tract. 1st ed. American Registry of Pathology; 2002.

· Priest JR, Williams GM, Hill DA, Dehner LP, Jaffé A. Pulmonary cysts in early childhood and the risk of malignancy. Pediatr Pulmonol. 2009;44(1):14-30.