CT findings of lung carcinoma

1. CA Lung- CT Findings
OSR
Dr. Yash Kumar Achantani

2. Solitary Pulmonary Nodule
Definition:
A focal lung opacity visible on chest radiographs or computed
tomography (CT) as a relatively well defined round or oval lesion
which is
• < 3cms
• Partially / fully surrounded by lung / pleura
• No lymphadenopathy / atelectasis / consolidation
Mass >3cms

3. SPN CT Approach
External Characteristics.
• Size.
• Shape.
• Location.
• Edge characteristics.
Internal Characteristics.
• Composition of nodule.
• Calcification.
• Cavitation.
• Air bronchogram.
• Feeding vessel sign.
• Positive Bronchus sign.
Growth rate Assesment.

4. Size
The size of the SPN is not a reliable indicator of benignity, although the
larger the nodule, the more likely it is to be malignant.
Diameter Malignancy rate
< 1 cm 35%
1-2 cm 50%
2-3 cm 80%
> 3 cm 97%

5. Shape
Irregular in shape
Lobulated or notched
Lobulation and notching - Indicate uneven growth and the more
pronounced the two signs, the more likely it is that the lesion is a
bronchogenic carcinoma.
Location
Adenocarcinomas - Peripheral SPNs
Squamous cell carcinomas - More likely to be centrally located.
Metastatic tumors presenting as an SPN - Subpleural or outer third of
the lung- Mostly in the lower lobes.

6. Edge Characteristics
Edge characteristics indicative of malignancy include irregularity,
spiculation and lobulation.
Exception - Metastases and Carcinoid tumors- Sharp and Smooth edge .
Corona radiata or the “sunburst appearance” - Presence of spiculation
associated with a nodule or a mass- Feature of malignant lesion.
Carcinomas may have “pleural tail” or “pleural tag” - thin linear
opacity is seen extending from the edge of a lung nodule to the pleural
surface.
The “halo” sign, a halo of ground glass opacity surrounding a nodule
may be seen in some patients with a malignant SPN. However it can also
be seen in some benign conditions.

7. Corona radiata sign in a malignant lesion with spiculation at the
margin.

8. HRCT showing a small dense spiculated central nodule surrounded by a halo of
ground glass representing the presence of lepidic tumor growth–Bronchioloalveolar
carcinoma showing the halo sign

9. INTERNAL CHARACTERISTICS OF A SPN
Composition
Solid and Ground-glass components.
Nodules containing a ground-glass component are more likely to be
malignant.
Partly solid lesions with ground-glass components- malignancy rate of
63%.
Nonsolid - only ground-glass lesions- malignancy rate of 18%.
Only solid lesions- malignancy rate of only 7%.

10. Partly solid nodule containing ground-
glass component most likely to be
malignant

11. Calcification
The most important imaging feature that can be used to distinguish
benign SPNs from malignant SPNs is calcification.
Benign patterns:-
i. Homogeneous calcification/uniform calcification
ii. Dense central (bull’s eye) calcification
iii. Concentric rings of calcium (target calcification)
iv. Conglomerate foci of calcification involving a large part of the nodule
(popcorn calcification)
Indeterminate Calcification
Stippled/punctate calcification or eccentric calcification may be seen in
benign SPN but may also be seen in cancers and is therefore considered
indeterminate.

13. Calcification in Tumor may be
1. Dystrophic calcification in areas of tumor necrosis
2. Diffuse and amorphous
3. Psammomatous calcification is seen in SPNs that are metastases from
mucin secreting tumors such as colon or ovarian cancers.
4. Central calcification in a spiculated SPN is suggestive of malignancy.
Cavitation
Both benign and malignant nodules can form a cavity. SPNs with
irregular walled cavities
Thicker than 16 mm tend to be malignant.
Less than 5 mm, 95 percent are benign.
5 to 15 mm, 75 percent are benign.
Malignant lesions- Thick, nodular wall
Benign lesions - Thin smooth wall.

14. Mediastinal window (A) showing a 10 mm nodule in the right lower lobe. Eccentric
cavitation is noted within.
HRCT section (B) shows the nodule to be spiculated, irregular and lobulated showing
the characteristic sunburst appearance – Bronchogenic carcinoma

15. Air Bronchograms and Pseudocavitation
On HRCT, air bronchograms are seen usually in cancers presenting as an
SPN.
Most typical of adenocarcinoma or bronchioloalveolar carcinoma.
Air Crescent Sign
Aspergilloma (mycetoma) is the most common cause of an air crescent
sign.
Other causes:
Blood clot in a cyst or cavity
Complicated hydatid disease
Carcinoma arising in a cyst
Cavitatory carcinoma
Mucous plug in a cystic bronchiectasis
Rasmussen aneurysm
Pulmonary gangrene
Gravitational shift of the intracavitary mass strongly suggest mycetoma
and excludes carcinoma.

16. Airbronchogram seen as a linear lucency (broad arrow) and as a more cystic
lucency (small arrow) due to the fact that the bronchus is seen en face.

17. Feeding Vessel Sign
A small pulmonary artery is seen leading directly to a nodule. It may be
seen with arteriovenous fistula, hematogenous metastasis or infarct.
Positive Bronchus Sign
This sign refers to a patent bronchus entering the nodule in which tissue,
typically bronchial carcinoma, infiltrates around but does not totally
occlude an adjacent bronchus. Thus a pulmonary lesion that directly abuts
or narrows a visible bronchial lumen is more likely to be malignant.

18. Follow-up CT scan in a post operative case of right renal cell carcinoma
Showing a small, smoothly marginated round solitary lesion in the left lung.
The lesion is seen at the tip of a small artery (feeding vessel sign) – Solitary
metastasis in renal cell carcinoma

19. CT scan of the chest showing a pulmonary lesion abutting
and narrowing the right upper lobe bronchus without
completely occluding it – The positive bronchus sign in
bronchogenic carcinoma.

20. Contrast Enhancement
No enhancement- Benign
Significant enhancement - >15 HU- Malignant.
Lung parenchymal window settings on chest CT (A) showing a small (< 1 cm) smooth
rounded lesion with a small pleural tail in the right upper lobe. Non contrast and contrast
enhanced scans with mediastinal window settings (B, C) showing no enhancement of
the lesion on the postcontrast scans – Benign lesion/tuberculoma

21. Lung parenchymal window settings (A) showing a small (1 cm) solitary lesion in the right
upper lobe. The lesion is irregularly marginated with spiculated contour and multiple
pleural tails. Non contrast and contrast enhanced scans with mediastinal window
settings (B, C) reveal significant enhancement > 15 HU on the postcontrast scans –
Malignant lesion

22. Growth Rate Assessment
Volume doubling time (VDT) is defined as the time required for a lesion to
double its volume.
VDT can be calculated if the time difference (t) initial volume(Vo) and
volume at time t (Vt) are known using the following relationship
VDT = [t × log 2]/log (Vt /Vo)
A 26 percent increase in nodule diameter is one doubling and a
doubling of diameter means that three volume doubling have occurred.
1- 18 months - Malignancy ( Exception: Bronchoalveolar carcinoma)
<1 month - Inflammatory and Infective (Exception: Sarcoma)
>18 months - Benign

23. Lung Mass CT Approach
Imaging features of the lung cancer largely depend on its
Location; central or peripheral.
Size,
Density of the tumor.

24. Peripheral Tumors
Peripheral tumors are those arising beyond the hilum or segmental bronchi.
Most Peripheral lung tumors are Adenocarcinoma and Bronchoalveolar Carcinoma.
 Round or oval mass lesion
 Well defined or ill defined.
 Lobulations and notching of the outline.
 Spiculated appearance - ‘corona radiata’ sign
 Doubling time between 1 and 18 months (Exception- Bronchoalveolar Carcinoma)
 When in segmental or distal bronchi may cause - Brochocele or Mucocele.
 Tumor Calcification- Engulfed Calcification- Amorphous or Cloudy- Central
Dystrophic Calcification- Peripheral
 Air bronchogram or bubble like lucencies - in adenocarcinoma or bronchoalveolar
carcinoma.
 Bronchoalveolar carcinomas may be seen as purely ground glass small nodules.

25. Peripheral lung cancer: CT scan shows the mass encasing the segmental
bronchus. A small pleural tail is seen extending from the mass to pleura

26. Corona radiata: An irregular lung mass is
seen with spiculated margins

27. Calcifications in lung cancer: (A) CT shows large lung mass with multiple, coarse
engulfed pre-existing granulomatous calcifications.
(B) CT of another patient shows a large lung mass with fine, amorphous tumoral
calcifications

28. Central Tumors
Most central lung cancers are squamous cell carcinomas.
 Central mass causing bronchial cut-off with or without collapse-
consolidation beyond it.
 Mostly are minimally enhancing soft tissue masses where as distal collapse
shows significant enhancement.
 Cavitation.

29. Squamous cell carcinoma: (B) CT scan of a patient shows Left lung cavity with
irregular and nodular wall thickening. There is abrupt cut-off of bronchus at the
tumor margin

30. (B) CT shows poorly enhancing
central lung mass with invasion of
aorta.
C) CT section at distal level shows
highly enhancing collapsed lobe with
mucus filled bronchi seen as multiple
cystic lucencies

31. Small cell Lung cancer
Highly malignant tobacco related cancer characterized by rapid growth and
early metastases.
 Characterized by bilateral hilar and mediastinal lymphadenopathy with or
without lobar collapse.
 Most primary tumors develop as small central tumor which rapidly spread
submucosally to involve vessels and lymphatics. This results in hilar mass.
 May or may not invade the bronchus.
 Invasion and thrombosis of SVC is common.

32. Small cell lung cancer: CT shows large mediastinal
lymphadenopathy with lung atelactasis (arrow). Multiple venous
collaterals are seen along right chest wall (arrowheads),
secondary to superior vena caval obstruction

33. Pulmonary metastases
Typically, metastases appear as- Soft tissue attenuation, well
circumscribed, rounded lesions, more often in the periphery of the lung.
They are usually of variable size.
Feeding vessel sign is a feature.
Pulmonary metastasis may be single in (Colorectal carcinoma,
malignant melanoma, skeletal sarcoma, testicular carcinoma,
adenocarcinomas in general)
Cavitation and Calcification although rare but can be seen sometimes.

34. Lung metastases from non seminomatous germ cell tumour of testis.
Seen as multiple opacities in both the lung fields.

35. Features of Consolidation on chest X-ray/ CT suspicious for lung
cancer
 Golden S sign
 Round or oval shape of the opacity
 Consolidation in the common bronchial territory
 Consolidation unchanged for more than 2 weeks
 Consolidation recurring at same site
 Expansion of the consolidated lobe
 Dilated fluid filled bronchi
 Visible stenosis or mass of the supplying bronchus