4. Definition of cyst
• Lung cyst is an air filled structure with
perceptible wall typically 1 mm in thickness
but can be up to 3 mm. The diameter of a lung
cyst is usually less than 1 cm.
• Usually containing air, but occasionally fluid or
solid material
5. Definition of cavity
• A gas-filled space which develops in an area of
pulmonary consolidation, mass or nodule .
• In comparison with a lung cyst, the wall of a
cavity is usually relatively thick (>4 mm).
6. Imaging Clues to Help Differentiate
Pulmonary Cysts and Their Mimics
Entity Imaging Characteristics
Lung cyst Well-circumscribed, rounded, thin-walled air-filled structure
within the lung parenchyma. Wall thickness of ≤3mm.
Cavity Air-filled space within the pulmonary parenchyma with
thicker walls (>4 mm).
Emphysema Polygonal-shaped lucent area without definable walls.
Bronchiectasi s Air-filled space within the lung parenchyma that
branches and connects with the airway. Associated airway
abnormalities including air trapping, bronchial wall
thickening, and bronchiolar impactions.
Honeycombi
ng
Clustered subpleural airspaces with variable size and wall
thickness. Other signs of pulmonary fibrosis: architectural
distortion, traction bronchiectasis, and reticular opacities.
7.
8.
9. • With the exception of centrilobular
emphysema, pulmonary diseases
characterised by cystic air spaces are
uncommon or rare conditions
10. • Unlike in other solid organs, the lungs do not
develop so-called simple cysts.
11. Diseases that may cause pulmonary
cysts
Centrilobular emphysema
Lymphangioleiomyomatosis
Langerhans cell histiocytosis
Lymphoid interstitial pneumonia
sjogren syndrome
Pulmonary metastases (squamous/adenocarcinoma)
Cystic fibrohistiocytic tumour of the lung
Subacute (± chronic) hypersensitivity pneumonitis
Barotrauma/ARDS
Pulmonary infection—pneumatocoeles
Desquamative interstitial pneumonia
Necrobiotic nodules (end stage)
neurofibromatosis
Birt-Hogg-Dubé syndrome (rare)
18. Pulmonary LCH
• In the early stages, nodules (which correspond
with Langerhans cell granulomas) are the
predominant features, while cysts tend to
develop later
19. • The combination of nodules, cavitating
nodules and cysts in a smoker should allow a
confident and accurate diagnosis to be made
on CT alone
21. Pattern o f cysts
• The cysts are typically diffusely distributed,
with a predominance in the lung apices and
relative sparing of the lung bases .
• Sparing of the medial tips of the middle lobe
and lingula .
• The cysts can have bizarre shapes and unequal
sizes
45. Centrilobular emphysema
• Most common type
• Irreversible destruction of alveolar walls in the
centrilobular portion of the lobule
• Usually upper lobe predominance and uneven
distribution
• Strongly associated with smoking.
46. CLE
• CLE is characterised by the presence of
multiple rounded areas of low attenuation,
which have diameters of several millimetres.
• The presence of a central core vessel
(centrilobular artery) in the low attenuation
cystic air space is classical of CLE
47. • Manifests as multiple small areas of low
attenuation without a perceptible wall,
producing a punched-out appearance
54. Lymphocytic Interstitial Pneumonia
• Benign lymphoproliferative disorder
• Diffuse interstitial infiltration of mononuclear
cells
• Not limited to the air ways as in follicular
Bronchiolitis
55.
56. LIP
• Rarely idiopathic
• In association with:
Sjögren‟s syndrome
Immune deficiency syndromes, AIDS
Primary biliary cirrhosis
Multicentric Castlemean‟s disease
57. LIP
• Ground-glass opacities and nodules are almost
universal features in LIP, with cysts seen in
about two-thirds of patients .
• Interlobular sepal thickening and reticular
opacities have also been reported .
• The lung cysts are usually small (less than
3 cm), thin walled and distributed in a
scattered, random distribution
58.
59.
60. Sjoegren disease
• Dry eye and dry mouth
• Fibrosis, bronchitis and bronchiolitis
• LIP
• Up to 40 time increased risk for lymphoma
(mediastinal adenopathy)
• 2 times increased risk for neoplasm
62. Sub-acute HP
• Cysts on HRCT are seen in approximately 10%
of patients with subacute HP and are usually
few in number and random in distribution.
63. • Despite their low frequency, the presence of cysts
can be a helpful clue in making a radiological
diagnosis of HP, when identified in conjunction
with the more classical signs of the disease: these
are centrilobular ground glass nodules and a
mosaic attenuation pattern.
• Furthermore, all of these signs of sub-acute HP
can be seen in the more chronic fibrotic form of
hypersensitivity pneumonitis
64.
65. C-isolated or scattered cysts with no
ancillary CT features
• Birt-Hogg-Dube syndrome [Folliculin gene-
associated syndrome ]
• Malignancy
66. Birt-Hogg-Dube syndrome
• This is a very rare condition that is associated
with pneumothoraces, renal cell carcinomas
and skin fibrofolliculomas
• Family history of recurrent pneumothoraces
• Reports suggest that there is a lower zone
preponderance for cysts in Birt-Hogg-Dube
