Solitary pulmonary nodule Dr Subash Pathak

1. An Approach to Solitary
Pulmonary Nodule
Dr Subash Pathak
1st Year Resident
Radiodiagnosis
NAMS

2. solitary pulmonary nodule
• Spherical intraparenchymal opacity 3 cm or less in diameter,
completely surrounded by lung parenchyma, without
associated mediastinal adenopathy or atelectasis
• (Haaga)
• Lesions > 3 cm are defined as masses; are considered
malignant unless proven otherwise.

3. • Radiological evaluation of SPN is one of the
-most common and
-most difficult diagnostic dilemmas in thoracic radiology.
• Detection and work-up of SPNs are critical because SPNs may
be malignant and lung cancer has an overall mortality rate of
up to 85%
• Prevalence has increased as a result of growing use of Chest
CT- especially its use to screen for occult lung cancer.
• Before detailed diagnostic evaluation ,determine whether
- Nodular opacity seen on C-Xray is real or artifact
• If real, whether it is SPN

4. • First to determine
• Is the lesion truly solitary?
• Is the lesion intrapulmonary?
• Is the lesion nodule?

5. Is the lesion truly solitary ?
• Dominant pulmonary nodule in X-ray may be associated with smaller
nodules.
• Careful search by CXR PA , lat view & in some cases CT may be
necessary.
• Multiple pulmonary nodules of similar sizes and appearance
- usu mets or granuloma
- require different evaluation than solitary
lesions.

6. Is the lesion intrapulmonary ?
• Intrapulmonary lesions
-discrete opacities at least moderately well marginated by aerated
lung on both frontal and lateral radiographs
• Pleural and mediastinal lesion
- base forms obtuse angles with lung and is not outlined by lung .

7. Other lesions mimicking intrapulmonary
nodules
- Skin lesions
- Chest wall lesions
- Bony islands
- Healing rib #
- Nipple shadow

9. Is the lesion nodule?
• Discrete round or oval opacity 4-30mm in diameter
• Linear and angular opacities are not nodules and represent scar or areas of linear
atelectasis.
• 3D analysis or volumetric CT can help to differentiate flat scar from true SPNs
• MILIARY – 2-4 MM [sutton]
• <2 mm - miliary
• 2-7 mm – micronodule
• 7-30 mm – pulmonary nodule
• >30 mm - mass

10. • Once SPN identified –radiologist should initiate
series of investigations
-to determine whether nodule is definitely benign
or suspicious form ( i.e. indeterminate)
A step wise approach is needed.
• The differential diagnosis of a solitary pulmonary
nodule is broad
• Management depends on whether the lesion is
benign or malignant and whether it is solid or
subsolid in attenuation.

11. Differential diagnosis: Solid SPNs
Type of cause Condition
Neoplastic (Malignant) Primary lung malignancies ( non-small cell, small cell, carcinoid,
lymphoma), Solitary metastasis, plasmacytoma
Benign mass Hamartoma, adenoma, neurofibroma, lipoma,fibroma
Vascular AVM, infarct and hematoma
Infection Granuloma (tuberculosis, histoplasmosis, sarcoidosis,
cryptococcosis), round pneumonia, abscess, septic embolus,
fungal infections, parasitic (hydatid/amebic abscess)
Noninfectious Amyloidoma, subpleural lymph nodule, rheumatoid nodule,
Wegener granulomatosis, focal scarring
Congenital Sequestration, bronchogenic cyst, bronchial atresia with
mucoid impaction

12. Differential diagnosis: Persistent Subsolid SPNs
Malignant:
• Lung adenocarcinoma (including preinvasive lesions, atypical adenomatous hyperplasia,
and adenocarcinoma in situ).
• Metastasis from melanoma
• RCC
• Adenocarcinoma of the pancreas, breast, and GIT
• Lymphoproliferative disorders.
Benign:
• Organising Pneumonia
• Focal interstitial fibrosis
• Endometriosis

13. Clinical evaluation
• Clinical estimation of risk of malignancy is important.
• Factors with increased risk of lung cancer:
• Patient’s age
• Presence of symptoms: Hemoptysis
• History of smoking
• History of exposure to asbestos, uranium, radon
• Family history: increased with h/o first degree relative with lung cancer.
• Past history: patient’s with history of malignancy and pulmonary fibrosis,
history of cancer who underwent resection of small nodules, increased risk of
malignancy even for smaller nodules.

14. Radiographic evaluation
• Chest X-ray
• CT /MDCT
• FDG PET
• MRI- in difficult to assess cases such as Pancoast tumors
• USG- guided biopsy for peripherally based SPNs
• TNB

15. CXR
• Initial examination.
• Most SPNs - incidental finding.
• Nearly 90% of newly discovered SPNs on chest
radiographs may be visible in retrospect on prior
radiographs
• Visualization of some nodules difficult due to
superimposed structures
• Poorer resolution than CT for calcification or size.
• Prior CXR imp study growth pattern

16. CT chest
The advantages of CT over CXR
• Better size estimation (diameter from largest cross-
sectional area or volume measurement)
• Better border resolution
• Hidden areas assessment - lung apices, perihilar regions,
and costophrenic angles
• Detection of multiple nodules
• Enhancement & nodule attenuation characterisation
• Staging of Malignancy possible
• CT can help guide needle biopsy
Cause of many SPNs will remain undetermined after initial
& thin-section CT exam. If nodule is at least 10 mm in
diameter CECT.

17. SPN characterstics:
• Size
• Location
• Shape
• Margin
• Calcification, air, fat, cavity
• Attenuation
• Enhancement
• Growth
• PET SUV
• Biopsy

18. Size
• 3 cm cutoff between mass and
nodule is defined as lesions >3
cm are usually malignant while
smaller lesions can be either
benign or malignant.
• Cohort study by Swensen et al
showed the relationship
between the size of a SPN and
the chance of malignancy in a
cohort at high risk for lung
cancer.
Size Total Malignancy
< 4 mm 2038 0%
4-7 mm 1034 1%
8-20 mm 268 15%
> 20 mm 16 75%

19. Location
• Malignancy:
• RT>Lt (1.5X)
• Upper lobes (70%)
• Squamous - central
• Adenocarcinoma- peripheral
• Metastatic - subpleural or outer 1/3rd of lung / 2/3rd in lower lobes
• IPF - lung cancer involve periphery of lower lobe, site in which fibrosis
is most likely to occur
• Benign nodules - equally distributed in upper and lower lobes.

20. Shape
• Benign lesions:
Polygonal (multifaceted)
Three dimensional ratio > 1.78
• Large three dimensional ratio
indicates relatively flat lesion:
sign of benignity.
• Lung carcinomas- irregular,
lobulated or notched.
• Hamartomas and metastasis-
round, oval and smooth with a
non-lobulated edge. Transverse image (left) and coronal reconstruction
(right)Three-dimensional ratio = transverse dimension :
vertical dimension

21. Margin
• Thin section CT more accurate than CXR
• Corona radiata sign: High association with
malignancy(PPV: 90%).
False positives include lipoid
pneumonia, focal atelectasis,
tuberculoma, PMF, pleural tail of
peripheral granuloma, organizing
pneumonia
• Lobulated or scalloped margins:
Intermediate probability
• Smooth margins: More likely benign;
exception,
Metastasis
20% of primary lung malignancies (adenoCa)
Carcinoid

22. Lobulated margins/ scalloped margins :
Intermediate Smooth margin: Benign

23. Calcifications
• Most important imaging feature to distinguish benign SPNs from
malignant SPNs
• CXR with low KVp and CT esp dual energy (more sensitive)
• In general, calcification implies benignity.
• SPNs < 9 mm rarely visible in CXR; if that sized nodule clearly seen
likely to be diffusely calcified and hence benign.

24. Calcifications
• Benign pattern
• Diffuse
• Central (bull’s eye) Granulomas
• Laminated
• Popcorn: Hamartomas
• Malignant pattern
• Punctate
• Amorphous
• Eccentric

25. • Exception: when the patient is known to have primary tumor
• Example:
• Diffuse calcification: Osteosarcoma/Chondrosarcoma
• Central/Popcorn calcification: Primary GI malignancy/ patients who
previously had chemotherapy.

26. CT: benign versus
malignant
Calcification
Benign:
seen in granulomatous diseases and
hamartomas.
• Diffuse
• Central
• Laminated
• Popcorn
• All other types of calcifications
do not indicate benignity.

28. Popcorn calcification- Hamartoma

29. Malignancy and calcifications
• Nearly 10% of malignant nodules- calcification in CT.
• Amorphous, stippled or eccentric pattern is seen most commonly in malignant
lesions
• Eccentric: benign/malig with dystrophic ca/engulfed benign calcified lesion
• Stippled: or psammomatous Ca mets from mucin secreting tumours as colon
or ovary
• Assess margin and size even if the lesion is calcified; central calcification in a
spiculated SPN should prompt concern for malignancy
• Malignant SPN with benign Ca in carcinoid, osteosarcoma, chondrosarcoma
 With the exception of SPNs in patients with a history of bone malignancy, SPNs
with a benign pattern of calcification are indeed benign.

30. Calcification patterns
CT scan in an 80-year-old man shows a
2.2-cm-diameter nodule in the left upper
lobe with eccentric calcification.

31. Fat attenuation (-40 to -120 HU)
Hamartoma with left lower lobe nodule
showing low attenuation -46 HU
• Causes:
• Lipoid pneumonia
• Hamartoma: 50% cases
• Pulmonary mets in RCC or
liposarcoma
• Demonstration of fat is difficult if the
nodule is small as partial volume
inclusion of lung may interfere with
attenuation measurements.

32. Air Bronchogram Sign
• Air bronchogram is more commonly seen
in malignant pulmonary nodules 29%
than in benign nodules 6%.
• Most common:
BAC (Bronchoalveolar cell
carcinoma)
Adenocarcinoma.
Lymphoma
Air bronchograms (bubble like lucncies/
pseudocavitation) may simulate cavities,
upto 55% BAC.
Represent desmoplastic reaction to tumor
that distorts airway.

33. Air fluid level
• s/o abscess

34. Cavitation
• Occurs in-
• Infections (abscess, infectious granulomas)
• Inflammations
• Vasculitides/pulmonary infarctions
• Malignancies, both primary and metastatic; more in Squamous cell type.
• Up to 15% of lung cancers cavitate but most are >3 cm.
• Cavitatory nodules
• Smooth and thin walls- Benign lesions ( < 5 mm – 92% benign)
• Thick and irregular walls- Malignant lesions ( > 15 mm – 95 % malignant)
• Wall thickness from 5-15 mm indefinite

35. Lung cancer manifesting as increased wall
thickness of cystic air space
77/m, right upper lobectomy for
adenocarcinoma, shows cystic air space in
the rt lower lobe
f/u CT after 6 mo shows new soft tissue
component along the wall/ increased wall
thickness

36. Solid and Ground glass component
• Studies show nodules containing a ground-glass component are more
likely to be malignant.
• Solid lesions: malignancy rate 7%.
• Partly solid lesions: malignancy rate 63%.
• Non-solid lesions: malignancy rate 18%.

37. Halo Sign
• CT feature showing poorly defined rim of ground glass attenuation
around the nodule.
• May represent: Hemorrhage, tumor infiltration or perinodular
inflammation.
• Originally described for invasive aspergillosis; also seen in:
• Adenocarcinoma in situ
• Kaposi sarcoma
• Lung mets from angiosarcoma, choriocarcinoma and osteosarcoma

38. Reverse halo sign
• Central area of ground glass attenuation surrounded by a halo or
crescent of consolidation.
• First described in cryptogenic organizing pneumonia.
• Can be seen in pts with lung cancer after radiofrequency ablation.
• Paracoccidioidomycosis, tuberculosis, lymphomatoid granulomatosis,
Wegener granulomatosis, sarcoidosis,

40. Reverse halo sign
63 y male with left lower lobe mets
from pancreatic ca 1 month after radiofrequency ablation

41. Percutaneous needle biopsy
• For peripheral nodules > 5 mm
• Under fluoroscopy or CT guidance/ USG if lesion abuts pleura
• Interpretation of FNAB specimens:
• Malignant
• Specific benign
• Nonspecific benign- further evaluation; may be malignant but
sample obtained outside nodule or from necrotic area.
• If further growth after nonspecific benign diagnosis, consider repeat
biopsy or resection.

42. Bronchoscopy
• For nodules located in the inner one third of the lung fields or in close
approximation to a bronchus on CT scans.
• Limited use in lesions < 2 cm.
• Lesions > 2 cm, the yield of malignancy varies from 40-69%
{malignancy risk ~75%}.

43. Thoracoscopy or thoracotomy
1. In patients with an indeterminate nodule and
a high probability of malignancy,
2. In needle Bx proven malignant nodule- -A
thoracotomy and lobectomy.

44. Subsolid SPNs
• Contain a portion of ground glass attenuation that is higher than that of
normal lung parenchyma and lower than that of soft tissue, such as blood
vessels.
• Can be:
• Pure ground glass attenuation Partly solid i.e. areas of soft
GGANs tissue attenuation interspersed
with ground glass attenuation

45. • Subsolid nodules may result from infection, inflammation,
hemorrhage or neoplasm.
• Inflammatory causes resolve at short-interval reassessment.
• Persistent subsolid nodules are more likely to be malignant; more
specifically lung adenocarcinoma.

46. Imaging
• CT techniques
• Challenging to detect SSNs due to their poorly defined margins and low
contrast relative to surrounding lung parenchyma.
• MDCT and post processing techniques improve the detection rates.
• Thin sections volumetric CT data helps assessing the 3D of the lesion and
helps differentiate from linear scarring or atelectasis.
• Thin sections avoid misinterpreting volume averaging from parenchymal,
mediastinal and chest wall structures as true SSNs.

47. CT findings and Morphology
• SSN detected reassess with CT at 3 months most
infectious or inflammatory origin may resolve or regress.
• If persistent, assess for other morphological features.
• Association with adenocarcinoma
• Are more likely to present as SSNs than other histological subtypes.
• The IASLC, ATS, ERS classification system uses multidisciplinary approach using
pathologic and imaging findings and molecular biology techniques.
• Non-mucinous and mucinous varieties.
• Non-mucinous varieties present as SSNs while mucinous varieties present as
solid nodule or consolidative changes.

48. Classification of nonmucinous forms of lung adenocarcinoma and CT
features of subsolid nodules
2011 IASLC, ATS, and ERS Classification CT Features
Atypical adenomatous hyperplasia GGAN
Adenocarcinoma in situ GGAN with a possible solid component
Minimally invasive adenocarcinoma GGAN, partly solid nodule
Lepidic predominant adenocarcinoma Partly solid nodule, solid nodule
Invasive adenocarcinoma classified by predominant
subtype
Partly solid nodule with a solid component, solid
nodule

49. Nodule attenuation
Nonsolid (GGAN):
• Inflammation
• Premalignant: AAH, AIS
• Malign: MIA, invasive
adenoca
Solid: most metastatic
nodules are solid
Partly solid:
solid component often contains
invasive adenocarcinoma

50. • Soft-tissue component of a subsolid nodule may represent an invasive
component and/or fibrosis with alveolar collapse.
• Currently, the degree of invasion is reported to directly correlate with
the size of the soft tissue component at CT.
• Various methods are investigated to quantify the degree of invasion
based on the soft tissue attenuation values.
• Comparing attenuation values of the solid component of the SSNs
with the pathological features shows significant higher attenuation
values in invasive than noninvasive/microinvasive.
• Proportion of solid to ground glass component of SSNs.

51. Figure 9b Fleischner Society recommendations for measuring subsolid lesions at CT. CT image obtained with wide and/or
lung window settings shows the ground-glass-attenuation component (arrowheads) of the lesion. Measurements are based
on the average of the long and short axis dimensions. Determination of the percentage of solid to ground-glass-attenuation
components is important, because the greater the solid component, the more likely that the lesion is an invasive
adenocarcinoma. * = solid component.
RadioGraphics,

52. Other morphological features
• Variable utility to differentiate benign from malignant.
• Size
• Unlike solid nodules, limited use.
• A study of resected persistent GGANs showed AAH had mean diameter of 8
mm, adenocarcinoma of 13 mm, and fibrosis (or organizing pneumonia) of 12
mm.
• Shape
• Round shape is more common in malignant subsolid nodules (65%) than
benign nodules (17%); in contrast another study showed round shape to
indicate AAH rather than adenocarcinoma.

53. • Notches in the nodule margin and pleural tags more frequent in
invasive adenocarcinoma than in MIA and AIS.
• Other features more frequent in malignant subsolid lesions are:
• Lobulations
• Spiculation
• Well defined but coarse interface
• Pseudocavitation or bubbly appearance (due to sparing of alveoli or bronchi
by tumor infiltration)

54. Assessment of Malignant Potential
• Nodule growth
• Nodule enhancement
• Nodule metabolism

55. Nodule growth
• Assessed on the basis of volume doubling time.
• Nodules being spherical, volume calculated by 4πr3
• Double the volume manifests as 26% increase in diameter in CXR
• Infectious/inflammatory nodules- doubling time < 20 days.
• Malignant solid SPNs have doubling time in the range of 20-400 days, usu <
100 days.
• Nodules with doubling time > 400 days are benign.
• Exception is subsolid adenocarcinoma which may take upto 1346 days
doubling time; so imaging reassessment is recommended for extended
time.
• For adenocarcinomas, range of volume doubling time is longest for GGANs,
then PSNs followed by solid lesions.

56. Exceptions
• Malignant SPN with short doubling time:
• Mets from choriocarcinoma, seminoma and osteogenic sarcoma
• Giant cell carcinoma, pulmonary carcinosarcoma and blastomas
• Associated with hemorrhage
• Malignant SPN with long doubling time: Carcinoid/ well-differentiated
adenocarcinoma
• Falsely large nodules;
• Adjacent inflammatory change, atelectasis, or scars
• Partial volume effect when thin sections CT not used

57. Limitations
• Limitations of use of DT to determine benignity of nodule
• Growth rate can’t be estimated in previously nonvisualised nodule (since
noncalcified nodules <1cm usually not visible in CXR)
• >35 yrs -pt should not be evaluated prospectively to determine benignity by
following growth rate ( do Bx)

58. Alternative to volume assessment in SSNs
• Mass measurement:
• CT data used to calculate X-ray attenuation values of SSN which is
proportional to tissue density i.e. mass per unit volume.
• Multiply nodule volume and density= mass.
• Allows detection of growth of SSN earlier and subject to less
variability than volume or diameter measurements.

59. Subsolid lesion in 56 yr old man which increased in size
CECT 1.3 cm nodule with pure GGA in
Left lower lobe
CT after 3 yrs size= 1.8 cm > double
volume

60. • Solid nodules with stable size over 2 years are considered benign.
• In case of SSNs, since the lesions are smaller and poorly defined
growth may be difficult to perceive.
• Unlike in solid nodules where growth is based only on size, in SSNs
growth may manifest as;
• Increase in size
• Increase in attenuation
• Development of solid component
• Increase in size of solid component
• These features indicate increased risk of malignancy

61. Increased attenuation in a SSN- indicator of possible malignancy
CT chest with coronal reformation
showing 1.2 cm SSN in left upper lobe
F/u image after 1 year shows increased
attenuation and increased size

62. Development of soft tissue component in a subsolid lesion:
increased risk of malignancy
CECT showing 1.8 cm nodule with pure
GGA in left upper lobe; pulmonary vessels
and air bronchogram sign are visible
F/u CT 3 months later showing new solid
component posteriorly/ turned out to be
adenocarcinoma

63. Temporary regression of SPNs
• Most lung cancers grow at steady exponential rate, however transient decrease
in size may occur attributed to development of fibrosis and subsequent
collapse of fibrosis.
• Continued reassessment warranted to confirm long term stability or regression.

64. Temporary regression of SPNs
• Initial presentation shows
nodule in left lower lobe
• 1 year f/u image shows
decreased size
CT at 2 years nodule show
increased size and lobularity

65. Nodule enhancement
• Applied for solid SPNs.
• Can be assessed for lesions as small as 5 mm.
• Degree of nodule enhancement correlates with the degree of vascularity,
which increases in malignant lesions.
• Malignant nodules enhance > 20 HU (less specific, exception active
inflammation), whereas benign lesions enhance < 15 HU.
• Nodules enhancing < 15 HU are definitely benign (NPV, 96%; sensitivity,
98%; specificity, 58%; accuracy, 77%).
• Limitations:
• Better for lesions < 2 cm (high chance of benignity/less likely to have substantial
necrosis).
• CT enhancement can be calculated only in lesions with a relatively spherical shape
and homogenous attenuation (i.e. no e/o fat, calcification, cavitation, or necrosis).

66. Nodular enhancement
CT 54/F with endometrial hyperplasia
Post contrast nodule enhanced with
attenuation value 109 HU; biopsy showed
carcinoid

67. Nodule metabolism
• Metabolism of glucose is increased in malignancies.
• This property is utilized in functional imaging with 18F labelled
fluorodeoxyglucose (FDG) positron emission tomography (PET) as an
alternative to nodule enhancement measurement in the evaluation of
solid SPNs.
• FDG standardized uptake value (SUV) is commonly used.
• SUV cutoff of 2.5 is used.
• Sensitivity and specificity around 90% in >/= 10 mm malignant
nodules.

68. Considerations
• SUV uptake needs to be interpreted taking into consideration the risk
factor assessment and imaging features i.e. pretest likelihood.
• Negative PET with low pretest likelihood (20%)= likelihood of malignancy
1% while negative PET with high pretest likelihood (80%)= likelihood of
malignancy 14%.
• PET is poor in evaluating GGANs and PSNs (sensitivity, 10%; specificity,
20%).
• Limited spatial resolution of PET so false negative findings in < 10 mm
nodules.
• False negative PET findings: Carcinoid tumors and adenocarcinomas.
• False positive PET findings (low PPV): Infection and inflammation.

69. PET negative neuroendocrine tumors
Unenhanced CT well circumscribed
nodule in the middle lobe
PET/CT show no FDG uptake; biopsy
revealed carcinoid

70. PET in subsolid lesion
57/M with thyroid and prostate ca, CT
shows 1.5 cm subsolid lesion in left lower
lobe with >5 mm soft tissue component.
PET/CT done preop shows no FDG uptake/
biopsy showed adenocarcinoma

71. PET in infections/inflammatory lesions
• 30/M, asymptomatic, unenhanced
CT shows 3 cm solid lesion in the
right lower lobe.
• PET/CT SUV uptake 16.7 2 month f/u CT regression of
the lesion/ biopsy
granulomatous inflammation

72. Decision analysis and management
• Guidelines by the Fleischner Society and American College of Chest
Physicians (ACCP).
• Considerations include:
• Patient’s clinical risk factors/risk stratification (significant risk include
older age, current or past history of smoking, h/o extrathoracic malignancy
> 5 yrs before nodule detection).
• Nodule characteristics on imaging (high likelihood of malignancy include
size, spiculation, and an upper lobe location).
• Comparison with previous images for nodule growth (solid nodule stable
for >2 yrs or with benign pattern of calcification no further f/u needed).
• Decision as to either observe or aggressive management is made on the
basis of the size of nodule and risk of malignancy.

73. Management options
• Serial reassessment at CT
• CT enhancement study
• FDG PET
• Histologic analysis
• For reassessment, unenhanced, thin-section, limited coverage, low-
dose CT is recommended.

74. Considerations while using guideline

75. Risk factors
• More parameters are added in the new 2017 guideline; more difficult.

76. Risk stratification

77. Algorithm for evaluation of solid SPNs

78. Updated 2017 guideline for solid pulmonary
nodules (2005)

79. Indeterminate lesions
• Indeterminate lesions:
• Not fitting in benign and malignant lesion.
• Most patients fall into this category.
• As many as 75% of these patients have malignant nodules on further
evaluation.
• Management decision
• Indeterminate –
• Percutaneous needle Bx
• Bronchoscopy
• Thoracoscopy or thoracotomy.

80. Subsolid nodule
• Unlike solid nodules, management options less clearly defined and
limited to serial reassessment and histological analysis.
• CT enhancement studies are not applicable.
• FDG PET limited use as these lesions have low metabolic rate.
• No use in pure GGANs; in part solid nodules can be used if solid
component is > 8 mm (ACCP)/ > 10 mm (Fleischner).
• ACCP considers pretest probability of malignancy while Fleischner do
not.
• ACCP considers overall nodule size while Fleischner only consider the
solid component size.

81. 2017 updated
guideline of Fleischner
Society
Differences from previous
guideline:
1. Earlier 5 mm cutoff was used.
2. F/u at 3 month for defining
persistent nodule has been
increased to 12 months.
3. Total f/u period is increased to 5
years from previous 3 years.

82. Algorithm for evaluating subsolid SPNs

83. Salient features of some lesions
presenting as SPN

84. Ca lung
• Adenoca and alveolar cell
ca
• Peripherally based SPN.
• Alveolar cell ca- air
bronchogram. Ground
glass appearance in CT.

86. Solitary metastasis
• 75% mets- Multiple
• 25% mets- Solitary
• Documented primary favours solitary
mets.
• An SPN is unlikely to be a mets in
absence of a known prior malignancy,
and a routine search for an extrathoracic
primary tumor is not cost-effective
• Common primary sites for sol mets
– Ca colon (1/3 of sol mets)
– Breast, kidney, testicular tumours, bone
sarcoma and malignant melanoma
• CT and CXR- no reliable features to
distinguish a solitary mets from primary
nodule.
SPN- A 1.5-cm lesion in left
upper lobe in pt with prior
colonic ca. Biopsy confirmed
this to be a metastatic
deposit

87. Hamartoma
• Malformation of tissue
normally found in organ
concerned.
• Large cartilaginous &
appreciable fatty component.
• 90% intrapulmonary origin.
• Incidental SPN- popcorn
calcification (30% cases), fat
density, peripheral location,
smooth or lobulated margin,
slow growth on serial
imaging.

88. Tuberculoma
• Mostly upper lobe
• Well defined. 25% lobulated margin.
• Calcification common (central or complete)
• Cavitation unusual.
• Satellite lesion common (80%)
• Usu size unchanged for years.

89. RoundPneumonia
• Spherical pneumonia caused by
• Haemophilus influenzae
• Streptococcus
• Pneumococcus
• Children are affected much more than adults
• Location
• Usually lower lobe
• Most often posterior
• May change size rapidly
• May have slightly irregular border and contain
air bronchogram

90. Lipoid Pneumonia
• Aspiration of mineral oil ingested by elderly to treat constipation
may produce localised pulmonary lesion.
• Radiologically
- a focal area of airspace opacification or a solid mass may be seen in
lower lobes.
- spiculated appearance may be due to inflammatory rxn leading to
fibrosis

91. Adenoma
• 90% around hilum
• 10% peripheral
• 25% SPN; 75% presents with effect of bronchial stenosis.

92. CT scan shows eccentric
dense calcification in a right
lower lobe carcinoid tumor.
Carcinoid tumors
• May present as SPNs
• Majority (80%) are
central endobronchial
lesions that presents
with atelectasis or
obstructive
pneumonias.

93. Summary
• Solid and subsolid SPNs are detected with increasing frequency
because of the widespread use of MDCT. Although most such
nodules are benign, lung cancer is a clinically important entity
in the differential diagnosis of SPNs.
• To ensure that appropriate treatment is initiated in a timely
fashion, the aim in evaluating SPNs is to correctly differentiate
malignant and benign lesions.
• Clinical assessment of patients’ risk factors for malignancy,
including age, smoking history, and history of malignancy, is
important .

94. • In terms of imaging evaluation, obtaining prior
radiographs or chest CT images is useful to determine
nodule growth.
• Further imaging evaluation, including CT
enhancement studies and PET/CT, helps determine
the malignant potential of solid SPNs.
• For solid nodules, CT enhancement of less than 15 HU
and low or no FDG uptake at PET/CT suggest
benignity.
• Awareness of potential pitfalls in nodule
enhancement and PET/CT evaluation of SPNs that
result from infectious or inflammatory conditions is
important to avoid misinterpreting imaging findings.

95. • For subsolid nodules, CT enhancement studies are not
applicable, and PET imaging is of limited use because of their
low metabolic activity.
• Because of the likelihood that persistent subsolid nodules
represent adenocarcinomas with indolent growth, serial
imaging reassessment for a minimum of 3 years and/or
obtaining tissue samples for histologic analysis are
recommended.
• At imaging follow-up of subsolid nodules, growth manifesting
as an increase in size, an increase in attenuation, development
of a solid component, or an increase in the size of a solid
component is suspicious for malignancy.

96. • Stratified according to patient risk factors for malignancy and nodule
characteristics, evidence-based clinical guidelines and
recommendations for the evaluation of solid and subsolid SPNs are
useful in decision analysis

97. References
• Update in the Evaluation of the Solitary Pulmonary Nodule
https://doi.org/10.1148/rg.346130092 RSNA article, October 2014,
Volume 34, Issue 6.
• Fleichner 2017 guideline for pulmonary nodules by Onno Mets and Robin
Smithuis, published on July 1, 2017.
• Solitary pulmonary nodule: benign versus malignant
• Differentiation with CT and PET-CT
• Ann Leung and Robin Smithuis
• Department of Radiology, Stanford University Medical Center, Stanford,
California and the Department of Radiology, Rijnland Hospital, Leiderdorp,
the Netherlands

98. Thank You