Honeycombing (lungs)

Honeycombing is a CT imaging descriptor referring to clustered cystic air spaces (between 3-10 mm in diameter but occasionally as large as 2.5 cm) which are usually subpleural and basal in distribution. They can be subdivided into:

• microcystic honeycombing:
• macrocystic honeycombing

The walls of the cysts are well-defined and often thick (1-3 mm) ⁴. They represent an irreversible finding commonly seen in diffuse pulmonary fibrosis (usual interstitial pneumonia).

Pathology

Honeycombing consists of enlarged airspaces with thick fibrotic walls lined by bronchiolar epithelium and often filled with mucin and inflammatory cells ⁶.

History and etymology

The term “honeycomb lung” is thought to have originated in the 19^th century in Germany and is thought to have first appeared in 1949 in a study by N Oswald and T Parkinson ⁵.

Differential diagnosis

• airspace consolidation in the presence of pulmonary emphysema can mimic this appearance
• in some situations, paraseptal emphysema and paracicatrical emphysema can also mimic honeycombing ³