Incidentally discovered pulmonary nodule are a diagnostic challenge. This presentation is focused on the different features of lung nodules and their management.

1. The solitary lung nodule: a
diagnostic dilemma.
Dr. Hazem Abu Zeid Yousef
Assistant professor of radiodiagnosis.

2. DEFINITION
A lung nodule is an opacity rounded or irregular, well or ill
defined, up to 3 cm in diameter, which is surrounded by
lung parenchyma at least two thirds of its margins, without
associated atelectasis, hilar thickening or pleural effusion.
Lesions greater than 3 cm are considered masses.
Nodules attached to the fissure or pleura, homogeneous, solid,
smooth contour, oval, lenticular, or triangular-shaped, are likely to
be benign nodules (intrapulmonary L.N or perilymphatic nodule).

3. PREVALENCE
The failure to recognize lung cancer on the CXR is one
of the most frequent causes of a missed diagnosis in
radiology.
The detection rate of a SPN is 0.09% to 7% on CXR.
A positive screen result in the CT arm of the North
American National Screening Trial (NLST) was defined as
finding a non-calcified nodule of at least 4 mm. Using these
criteria 27% had a positive baseline screen. The
Netherlands-Belgium Lung cancer Screenings Trial (NELSON
study) showed a rate of 51% at baseline.

4. The major question that follows detection of a
solid SPN is whether it is benign or malignant.
Prevalence of malignancy in a SPN:
As screening programs are typically performed in
developed countries, the prevalence of malignancy
in single pulmonary is ranging from 1% to 12%.

6. General evaluation of SPN
Patients with a newly diagnosed SPN should
undergo an initial diagnostic interdisciplinary
evaluation based on radiological and clinical
findings to determine the probability of being a
malignant nodule.
The assessment involves risk stratification of the
individual patient, performing further imaging
studies, and formulating a management plan
taking into consideration the risks associated with
various treatment strategies and the individual
patient preferences.

10. Clinical characteristics
Older age, smoking, female gender, asbestos
exposure and previous history of cancer all
increase the probability that a solid SPN is
malignant. The presence of underlying lung
disease such as emphysema, fibrotic lung
disease (idiopathic pulmonary fibrosis, radiation
and asbestosis) are additional risk factors.

11. Chest Radiograph (CXR)
CXR is the most frequently used first-line imaging
tool for diagnosis of cardiopulmonary disease. The
sensitivity and specificity of chest radiographs are
well known to be inferior to CT for lung nodule
detection. Suboptimal patient positioning and poor
inspiratory lung volumes can hinder detection of
lung nodules. Overlying bones in addition to the
heart, hilum, and diaphragm, obscure portions of
the lung. Due to numerous overlying bones, the
lung apex is one of the most difficult areas to detect
a lung nodule on chest radiograph .

13. Computed Tomography (CT)
General Recommendations
All chest CT scans should be reconstructed and
archived with contiguous thin sections (typically
1.0 mm) to enable accurate characterization and
measurement of small pulmonary nodules.

15. Mediastinal and lung window settings.

16. Axial, sagittal and coronal series.

17. Nodule size measurement.
Since 2005, the Fleischner Society recommended use of
the average diameter, as the average of long and short
axes measured by using lung windows. For larger
nodules and for masses larger than 10 mm, it is
generally appropriate to record both long- and short-
axis dimensions.

18. Using low dose technique.

19. Computed tomography imaging
features
Lung nodules are classified into:
1) Solid nodule.
2) Pure ground glass nodules (GGN): nonsolid
density through which normal lung architecture
remains visible.
3) Part solid nodules (PSN): composed of both solid
and nonsolid components.
In a screening study by Henschke et al malignancy was
found in 13% of non-solid lesions, 32% of solid lesions
and 63% of partially solid lesions.

24. CT imaging features
Internal
structure
Air bronchogram
P. angiogram
Cavitation
Calcification
Fat density
Halo sign
Inverted halo sign
Marginal
characteristics
Spicula
Notch
Pleuralindentation
Pit-fall sign
Specific lesions
Air-crescent sign
Comet tail sign
Feeding vessel sign
Sarcoid galaxy sign
Nodule location
Nodule size
Volume doubling
time

25. Nodule size:
The likelihood of being malignant is greater in larger
nodules. Studies have found that up to 80% of SPNs
larger than 2 cm may be malignant and that over 90%
of nodules less than 2 cm are benign. Further studies
indicate that < 1% of nodules with a diameter < 5 mm
in patients without a history of cancer will demonstrate
malignant behaviour.

26. Volume doubling time:
If a solid nodule is unchanged over 2 years, the nodule is
typically considered benign. Benign lesions tend to grow very
slowly or to remain stable in size, whereas most untreated
malignant lesions will grow rapidly. The use of serial volume
measurements rather than serial diameters more accurately
assess nodules. Small increases in size are easier to detect
with volume measurements. Assuming a spherical shaped
nodule the volume is related to the diameter by the equation
𝑉 =
4
3
πr3 . For example, an increase in diameter of 26%
corresponds to a volume increase of 100%.

28. Follow up CT
14months later

29. Nodule location:
the probability of malignancy is greater if the nodule is
located in upper lobes than on the lower lobes.
When they are just attached to the fissure, they are
homogeneous, solid, smooth contour and oval,
lenticular, or triangular-shaped, and it is likely to be
benign nodules (possibly intrapulmonary lymph nodes).

30. Sub-pleural/perifissural nodule:
The prevalence of perifissural nodules can be as
high as 20%, as has been observed in lung
cancer screening populations. When perifissural
nodules demonstrate a triangular or lentiform
morphology, smooth contours, and sharp
margins, they are known to represent
intrapulmonary lymph nodes and are considered
to be benign.

32. If a nodule adjacent to the pleura or a fissure
demonstrates a round morphology or contour
irregularity and/or the adjacent fissure is
abnormal (retracted, bowed, or transgressed),
follow-up CT at 6–12 months is indicated.

34. Signs of internal structure
Air bronchogram:
Phenomenon of air-filled bronchi being made visible by
the opacification of surrounding
alveoli.
Air bronchogram on chest radiograph is an important
sign to describe a feature of
airspace consolidation, but it is rarely used for nodular
lesion

36. CT air bronchogram:
The CT air bronchogram sign seen in solitary pulmonary
nodules is more common in malignant than in benign
lesions.
In small lung adenocarcinomas, AIS (adenocarinoma in
site) and MIA (minimally invasive adenocarcinoma) are
characterized by air containing structures, which are
differentiating features from invasive adenocarcinoma3.
However, focal organizing pneumonia also shows air
bronchogram. MALT lymphoma can also present as a
nodule or consolidation with air bronchogram.

37. Adenocarcinoma

38. MALT lymphoma

39. CT angiogram:
CT angiogram sign consists of enhancing branching
pulmonary vessels in a homogeneous low attenuating
consolidation of lung parenchyma. The sign can be
observed in pulmonary consolidation of varying
etiologies.

40. Invasive mucinous
adenocarcinoma

41. MALT lymphoma

42. Cavitation:
Cavitation occurs in both benign and malignant
lesions. The thickness of the cavity wall is a
useful determinant of malignancy; irregular thick-
walled >16 mm cavitatory lesions are strongly
associated with malignancy, however unless the
wall is over 5 mm in thickness then the distinction
between benignity and malignancy is not marked

45. Transverse 1-mm CT sections obtained 10 months apart show a highly
suspicious pattern of progressive thickening in the wall of a right lower
lobe cyst (arrow). Resection revealed invasive adenocarcinoma

46. Fat density:
Fat containing lesions are usually benign. The most
common fat containing pulmonary lesion is a
hamartoma. Fat density is seen in 34% of
hamartomas on CT, and in 19% both fat and calcium
are detected. There are however several malignant
lesions which are fat containing, for example
metastases from liposarcoma and renal cell
carcinoma.

47. Pulmonary
hamartoma

48. Calcification:
Six common patterns are shown in the next slide. The
first four are virtually always indicative of benignity,
whereas the other two may occur in benign or
malignant nodules.

49. Central Laminated Diffuse
Pop-corn Stippled Eccentric

51. CT halo sign:
CT halo sign is characterized by ground glass opacity
surrounding a pulmonary nodule or mass. This finding
was first described in patients with angioinvasive
aspergillosis; however, it can be seen in many other
pathological conditions such as infection, neoplastic
and inflammatory diseases.

52. Angioinvasive
aspergillosis

53. Adenocarcinoma

54. Reversed halo sign:
A reversed halo sign represents a nodule, which
has central ground-glass opacity surrounded by
consolidation. This sign has been described as a
finding in organizing pneumonia

55. Cryptogenic organizing
pneumonia

56. Signs of marginal characteristics
Spicula:
These are linear strands extending from the
margin of nodules into the lung parenchyma but
not extending to the pleura. Spicula is one of the
characteristic findings in malignant nodules.
This finding, however, can also be seen in benign
nodules in the presence of emphysema.

57. Adenocarcinoma

59. Notch:
Notch is defined as an abrupt bulging of the
lesion contour. Malignant nodules generally
have irregular spiculated margin with notch or
lobulation. The Rigler notch sign refers to an
indentation in the border of a solid lung mass at
a feeding vessel, in rapidly growing tumors, such
as peripheral squamous or large cell carcinoma.

60. Peripheral squamous cell carcinoma

61. Pleural indentation
Pleural indentation (or pleural tag) consists of a linear
opacity that extends from a peripheral nodule or mass
to the visceral pleura. Although they are associated
most commonly with adenocarcinoma, they may be
seen with other histologic subtypes; they also may be
identified in pulmonary metastases and granulomas.

63. Pit-fall sign:
Pit-fall signs refer to multiple linear strands between
the nodule and pleura. Adjacent normal lung expands
to fill the dead space between the retracted visceral
pleura.
The pit-fall sign suggests a possible pleural involvement
correlated with a poor prognosis.

65. Signs of specific lesions
“Air-crescent sign"
refers to the
crescent of air
seen in invasive
aspergillosis, or
other processes
with necrosis.

66. A "comet tail sign" is
produced by the
distortion of vessels
and bronchi that
lead to an adjacent
area of rounded
atelectasis on CT.

67. Feeding vessel sign
consists of a distinct
vessel leading directly
to a nodule or a
mass. This sign
indicates either that
the lesion has a
hematogenous origin.
A number of
hematogenous non-
neoplastic disorders
of the lung can show
this sign, e.g.
•Pulmonary vasculitis
•Pulmonary
infarction.

68. Parenchymal nodules in
pulmonary sarcoidosis
shows a characteristic
pattern resembling a
galaxy “pseudoalveolar
appearance” caused by
coalescent granulomas

69. Contrast enhancement
Enhancement on CT:
Malignant lesions usually have a higher vascularity than
benign nodules as the degree of enhancement is directly
related to the blood flow. Using a contrast enhancement
threshold of greater than 15 HU had a sensitivity of 98%,
specificity of 58% and accuracy of 77% for malignancy.
The specificity is low because inflammatory and
granulomatous lesions can also enhance. The negative
predictive value is high (96%) therefore absence of
enhancement of greater than 15 HU is strongly predictive
of benignity.

70. Revised Fleischner Society
Guidelines
Since their introduction in 2005, the Fleischner
Society released guidelines for the management
of incidentally detected pulmonary nodules,
these guidelines have been widely adopted. The
main purpose of the Fleischner Society
guidelines is to decrease the number of
unnecessary follow-up examinations performed.

71. The Fleischner Society guidelines for nodule
management released in 2017 are more
comprehensive and inclusive and are based on a
better understanding of the morphologic
features of pulmonary nodules, reliable size
measurements, the recognition of subsolid
components, an understanding of interval
growth or change in nodule morphology, and
knowledge of patient risk factors.

72. The Fleischner guidelines: Who is it for?
• Immunocompetent.
• Age 35 and above.
• Without pre-existing cancer.
• Not meant for lung cancer screening.
• The dimensions are average of long and short
axes.

75. Recommendation for Solid Lung Nodules <6 mm
• Single solid noncalcifed nodules <6 mm do not
require routine follow-up in patients at low risk.
• Solid nodules smaller than 6 mm do not require
routine follow-up in high risk patients however;
some nodules smaller than 6 mm with suspicious
morphology, upper lobe location, or both may
warrant follow up at 12 month.

76. Recommendation for Solid Lung Nodule 6-8 mm
• Patients with low clinical risk are recommended
to undergo initial follow-up at 6–12 months
depending on size, morphology, and patient
preference.
• Patients with high clinical risk are recommended
to undergo initial follow up at 6-12 months and
again at 18-24 month.

77. Recommendation for Solid Lung Nodules >8 mm
Consider 3-month follow up, work-up with PET and
CT (PET/CT), tissue sampling, or a combination
thereof.

78. Recommendation for multiple solid noncalcified
nodules: <6 mm
• For multiple solid noncalcified nodules < 6 mm in
diameter, no routine follow-up is recommended.
• In patients at high risk, a 12 month follow-up
examination may be considered.

79. Recommendation for multiple solid noncalcified
nodules: ≥6 mm
• For multiple solid noncalcified nodules with at
least one nodule ≥6 mm, follow up is
recommended at approximately 3-6 months.
• This is followed by an optional second scan at
18-24 months that will depend on estimate
risk.

80. Recommendation for pure ground-glass nodules
<6 mm
• For pure ground-glass nodules < 6 mm, no
routine follow up is recommended.
• Two and 4 year follow-up in selected subjects at
high risk.

81. Recommendation for pure ground-glass nodules
≥6 mm
• For pure ground-glass nodules ≥6 mm, follow-
up scanning is recommended at 6-12 months
and then every 2 years thereafter until 5 years.

82. Recommendation for part-solid nodules <6 mm
For solitary part-solid nodules <6 mm, no routine
follow up is recommended.

83. Recommendation for part-solid nodules ≥6 mm
solid component <6 mm
For solitary part-solid nodules ≥6 mm with a solid
component < 6 mm in diameter, follow up is
recommended at 3-6 months and then annually for
minimum of 5 years.

84. Recommendation for part-solid nodules ≥6 mm
solid component >6 mm
For part-solid nodules with a solid component ≥ 6
mm, a short-term follow-up CT scan at 3-6 months
should be considered. For nodules with suspicious
morphology, a growing solid component, or a solid
component larger than 8mm, PET/CT, biopsy or
resection are recommended.

85. Recommendation for multiple subsolid lung
nodules <6 mm
• In patients with multiple subsolid nodules <6
mm, consider infectious causes.
• If lesions persist after an initial follow-up scan
at 3-6 months, consider follow-up at 2 and 4
years to confirm stability.

86. Recommendation for multiple subsolid lung
nodules ≥ 6 mm
In patients with multiple subsolid nodules with at
least one nodule that is ≥ 6 mm, management
decision should be based on the most suspicious
nodule.

87. TAKE HOME MESSAGES
• The use of thin (1.0–1.5-mm) sections is essential for
the characterization of solid and subsolid pulmonary
nodules and the detection of calcium or fat; these
features can lead to different management options.
• The size and morphology of a pulmonary nodule are
the two primary determinants of cancer risk.
Morphology refers to the margins (smooth,
lobulated, or spiculated) and attenuation (solid,
partly solid, or purely ground glass) of the nodule.
• Older age, heavy smoking, larger nodule size, upper
lobe location, and/or nodule margin irregularity or
spiculation increases the risk of cancer.

88. Level of suspicion
• Young patient, incidental finding, no risk
factors, no symptoms: observation reasonable
• Older patient, acute symptoms, risk factors
present: treatment and surveillance
reasonable
• Older patient, no symptoms, high risk factors:
more complex situation.

89. THANK YOU.