For quick reference you can learn this ppt in short period of time. 4 main d/d is discussed with beautiful CT-Scan findings.

1. DIFFERENTIAL DIAGNOSIS
OF PULMONARY CYST
Dr. Bijay Kumar Yadav
MD-Radiology Resident
I.K. Akhunbaev KSMA

2. Pulmonary Cyst:
• Pulmonary cysts are round, thin-walled,
low attenuation spaces/lucencies in the
lung.
• Lung cysts usually contain air but
occasionally also contain fluid or solid
material.
• Pulmonary cysts can be congenital or
acquired.

3. Differential Diagnosis Of pulmonary Cyst
1. Bullous Emphysema
2. Cystic Bronchiectasis
3. Histiocytosis (Pulmonary Langerhans cell Histiocytosis)
4. Pneumatoceles

4. 1. Bullous Emphysema
• BULLOUS emphysema is usually associated with
strictures of the bronchi. These narrowed bronchi permit
the inspired air to enter the alveoli, but on expiration the
outlet closes and back-pressure is created,
• A mechanism which in time causes dilatation, atrophy,
& rupture of the alveoli.
• Finally, large emphysematous bullae evolve from the
coalescing alveoli.

5. Emphysematous Changes More On The Right Side With Apical Bullae

6. Axial CT Bullous Emphysematous

7. Saggital Bullous Emphysematous

8. Coronal Lung Window Bullous Emphysema

9. Severe Bullous Emphysema

10. Bullae Cyst

11. 2. Cystic Bronchiectasis
• Cystic bronchiectasis is one of the less common
morphological forms of bronchiectasis.
• It may be present on its own or may occur in
combination with other forms of bronchiectasis.
• Bronchiectasis is defined as an irreversible abnormal
dilatation of the bronchial tree. It has a variety of
underlying causes, with a common aetiology of chronic
inflammation.
• According to macroscopic morphology, Bronchiectasis is
of three types.
a. Cylindrical bronchiectasis :
b. Varicose bronchiectasis :
c. Cystic bronchiectasis :

12. Radiographic features:
• It is characterized by saccular dilatation of
bronchi that extends to the pleural
surfaces. When aggregated these may give
a "bunch of grapes" like appearance.

13. Cystic Bronchiectasis

14. Cystic Bronchiectasis Causing Pneumothorax

15. Multiple Diffuse Cystic Dilatation Of The Bronchioles

16. 3. Histiocytosis
Pulmonary Langerhans cell histiocytosis (PLCH):
• May be seen as part of widespread involvement in patients
with disseminated Langerhans cell histiocytosis or more frequently
as a distinct entity in young adult age group 20-40 years smokers.
• In adults, PLCH is most common & the lung is the most common
and often only organ involved.
Radiographic Findings:
• Thin-section computed tomography (CT) performed during early-
stage disease shows ill-defined 1–10-mm centrilobular nodules that
may be cavitary.
• As disease progresses, cystic lesions predominate over nodules.
• Cysts may be thin or thick walled and often have irregular & bizarre
shape.

17. PLCH in a 44-year-old woman.
(a) Axial thin-section CT image shows poorly defined nodules
predominantly in the upper lobes (arrowheads), typical of the early
cellular stage of PLCH. Some nodules have central lucency, indicating
developing cysts (arrows).
(b) Axial thin-section CT image shows spared lung bases.
(a) (b)

18. PLCH in a 31-year-old man.
Axial (a) and coronal reformatted (b) thin-section CT images show
irregular cysts of variable thickness and size (arrow) in the upper lobes
and sparing of the lung bases.
(a) (b)

19. PLCH in a 28-year-old man.
(a) Axial thin-section CT image shows bizarrely shaped cysts (arrow)
in the upper lobes.
(b) Two-year follow-up axial thin-section CT image obtained after
chemotherapy for systemic LCH shows smaller cysts (arrow).

20. PLCH in a 25-year-old man.
Axial thin-section CT image shows irregular cysts (arrow) of variable
size in the upper lobes and pneumothorax on the left side (★).

21. 4. Pneumatoceles
• Pneumatoceles are intrapulmonary gas-filled cystic
spaces that can have a variety of sizes and appearances.
• They may contain gas-fluid levels and are usually the
result of ventilator-induced lung injury in neonates or
post-infectious.
• Although pneumatoceles are seen in all age groups, they
are most frequently encountered in infant.
• The majority of pneumatoceles occur as a result
of pneumonia also due to blunt trauma.

22. Radiographic features: CT Scan
• Smooth inner margins
• Little if any fluid content
• The wall, if visible, is thin and regular
• Tend to persist despite an absence of symptoms.

23. Pneumatoceles developing in 13-year-old boy with staphylococcal pneumonia.
A) CT scan shows thick-walled pneumatoceles (white arrows) in the early
phase of pneumonia in the right upper lobe.
B) in another patient, follow-up CT scan obtained 20 months after initial
infection shows numerous residual pneumatoceles (white arrows) in the right
lower lobe.

24. Traumatic Pneumatocele