This document outlines the approach to evaluating a solitary pulmonary nodule (SPN). It defines an SPN as a rounded opacity less than 3cm surrounded by lung tissue. About 40% of SPNs are malignant. The workup includes reviewing prior imaging, CT scan, PET scan, and biopsy if needed. Features like size, margins, calcification, cavitation, and growth rate provide clues about malignancy, but biopsy is often necessary for a definitive diagnosis. The goal is to accurately differentiate benign from malignant lesions to guide treatment.

1. APPROACH TO SOLITARY
PULMONARY NODULE
DR. SIDDHARTH

2. OUTLINE
• INTRODUCTION
• SPN
• ETIOLOGY
• IMAGING MODALITIES

3. DEFINITION
• A solitary pulmonary is defined as a discrete,
well marginated, rounded opacity less than or
equal to 3cm in diameter that is completely
surrounded by lung parenchyma does not touch
the hilum or mediastinum and is not associated
with adenopathy, atelectasis or pleural effusion.
• About 40% malignant
• Lung mass: greater than 3 cm
▫ Vast majority are malignant

4. ETIOLOGY-COMMON CAUSES
• Bronchial Carcinoma
• Benign Lung Tumor – Hamartoma (commonest)
• Infective Granuloma, Tuberculoma, Fungal
granuloma
• Pulmonary metastasis – Breast, sarcoma,
Aminoma, Hypernephroma
• Lung Abscess

5. LESS COMMON CAUSES
• BENIGN TUMORS
• Hamartoma
• Bronchial Adenoma
• Chyloductoma
• Chondroma
• Fibroma
• Hemangioma
• Leiomyoma
• Papilloma
• Thymoma

6. OTHER MALIGNANT TUMORS
• Alveolar cell Carcinoma
• Lymphoma
• Mesothelioma

7. CHEST WALL LESIONS
• AV malformation
• Lipoma
• Fibroma

8. CYSTS
• Bronchogenic
• Hydatid
• Endometriosis
• Foreign Body infection

9. MYCOSIS PARASITOSIS
• Aspergillosis
• Coccidiodomycosis
• Histoplasmosis
• Nocardiosis
• cryptoccosis

10. MISCELLANEOUS
• Intra pulmonary lymph node
• Pulmonary infarct
• Pulmonary Sequestration
• Post Traumatic Hematoma
• Rheumatoid nodule
• Wegners granuloma

11. • Simulants of a solitary pulmonary nodule
External object
Pseudotumor (fluid in fissure)
Pleural plaque or mass

12. PRIMARY GOAL
• The goal of radiologic evaluation of suspected
solitary pulmonary nodules is to noninvasively
differentiate benign from malignant lesions as
accurately as possible

13. • Standard radiologic evaluation of a suspected
solitary pulmonary nodule includes careful
review of findings at chest radiography and,
when appropriate, comparison with findings at
prior radiography, chest fluoroscopy, and CT
and correlation with clinical signs and symptoms

14. WORK-UP OF SPN
• CXR
• Sputum Examination
• CT Scan
• PET Scan
• Bronchoscopy
• Biopsy
▫ TTNA, FNA
▫ VATS, Open

15. LESION DETECTION
• Pickup - this is a variable factor depending on
the radiologist’s experience
• Over reading / under reading
• High kV - better rate of detection
• Digital radiograph - this allows manipulation on
a computer monitor and a higher rate of
detection

16. • Lateral films for “hidden” lesions

17. Extrapleural Pleural Intrapulmonary

18. IS IT BENIGN OR MALIGNANT?
Start with
• Clinical History
• Age- Risk of Malignancy increases with age
• Sex
• Individual habits- smoking
• Familial history- malignancy

19. • Morphology of nodule
• Rate of growth
▫ Serial follow up
▫ Doubling time

20. Doubling Time
• 25% increase in diameter results in doubling of
volume
• Non-malignant disease: less than 1 month or
greater than 400 days
• Malignant lesions: 30 to 400 days

21. Morphology of nodule
▫ Size
▫ Location
▫ Margin/edges
▫ Contour
▫ Density/attenuation

22. ▫ Cavitation
▫ Calcifications
 However none of these can alone distinguish a
benign nodule from malignant.

23. SIZE
• Has a very limited role in evaluating the nature of lesion
• SPN is evident on cxr only if size is >9mm
• Nodule measure 0.5 to 1cms – 68% benign
1 to 2 cms – 50% benign
2 to 3 cms – 80% malignant
>3 cms - 97% malignant
• However micronodules <5mm may have a very high
malignant potential.
• Chances for malignancy increases as the size of the
nodule increases.

24. LOCATION
• Attached nodule-contact surface of nodule >50%
of diameter attached to fissure /pleura/vessel is
benign.
• Purely intraparenchymal-
▫ Primary ca - mostly upper lobes(mostly right)
▫ Metastatic SPN- outer one-third of lung fields
▫ Benign – equal distribution in upper and
lower lobes

25. MARGINS/EDGES
• Benign
▫ Smooth
▫ Lobulated-indicates an organizing mass
 60% malignant
• Malignant
▫ Irregular
▫ Speculated –corona radiata/sun burst
▫ Pleural tail/tag

26. • Spiculated Corona radiata sign
Fine linear strands extending
4-5 mm outward

27. • The CT halo sign indicates ground-glass attenuation
surrounding a pulmonary nodule. The halo of
ground-glass attenuation pathologically represents
pulmonary hemorrhage, tumor infiltration, or
nonhemorrhagic inflammatory processes.
• Initially, the sign was regarded as a specific sign of
invasive pulmonary aspergillosis, but it has a wider
differential diagnosis and can be caused by a variety
of other conditions such as infection, neoplastic, and
inflammatory diseases.

28. Positive bronchus sign
• A positive bronchus sign is a CT concept where a
hypoattenuating tube (bronchus) leads directly
to a lung nodule.
• The hypoattenuating tube may extend into the
tumor. Although the sign is not specific for a
malignant lesion, its presence indicates that a
high yield would be obtained by a transbronchial
biopsy

30. CT SCAN
• The advent of CT has led to improved
recognition of the frequency with which
nodules are nonsolid, partly solid, and solid.
Aerated lung parenchyma is visible through a
nonsolid (ground-glass) nodule, while a partly
solid nodule contains solid regions that mask an
aerated lung

31. • Partly solid nodules are more likely to be
malignant than nonsolid nodules
• Although solid nodules are the most common
type of nodule, they are less likely to be
malignant than are partly solid or nonsolid
nodules.
• Inflammatory diseases of the lung, particularly
tuberculosis and mycoses, usually produce solid
nodules that may eventually calcify and permit
the designation of benign disease.

32. CAVITATION
• Cavity – gas filled space may or may not be
accompanied by a fluid level.
• Thin <4mm & smooth walls – Lung abscess /
benign lesion.
• Thick >16mm and irregular – malignant lesions.
• When a cavity contains a mass within it will
form a crescent of air in between the mass and
the cavity wall – Meniscus sign.
• Seen with fungal balls (mycetoma) / abscess/
necrotic neoplasms.

33. CALCIFICATION
• HRCT is 10-20 times more sensitive than cxr

34. • Calcified SPN Cavitating SPN

35. • Malignant nodule
▫ Stippled
▫ Punctate
▫ Eccentric
▫ Central calcification in spiculated SPN

36. PET Scan
• 18-FDG (fluorodeoxyglucose)
▫ increased uptake by metabolically active cells
▫ does not enter glycolysis
• Allows more accurate identification of tumors,
lymph nodes, and metastatic disease
• Benign disease Malignant disease
▫ 96% sensitivity 96% sensitivity
▫ 88% specificity 77% specificity

37. Limitations of PET Scans
• Spatial resolution 7-8 mm thus unreliable for
lesions less than 1 cm
• False positives in infection or inflammation
• False negatives in tumors with low uptake such
as bronchoalveolar cell carcinoma

38. Bronchoscopy
• Limited role
• Transbronchial needle aspiration of mediastinal
lymph nodes
• Useful for large central lesions and
endobronchial lesions
• Can detect infection
• No use in peripheral nodules

39. Biopsy
• CT guided
▫ Transthoracic needle aspiration (TTNA)
▫ Fine needle aspiration (FNA)
• Surgical
▫ Video Assisted Thoracic Surgery (VATS)
▫ Open

40. TTNA
• Increasing utilization of TTNA
• Not indicated for patients committed to surgery
• Accuracy for detecting malignancy 64-100%
• Yield increased when cytopathologist present
• Three results:
▫ Malignant
▫ Specific benign, e.g. TB
▫ Non-specific benign, e.g. bronchoalveolar hyperplasia

41. Surgical biopsy
• VATS (Video Assisted Thoracic Surgery)
▫ peripheral nodules within 2 cm of pleura
▫ solid lesions
▫ lesions not diagnosed by other means
• Open
▫ commitment to resection with curative intent

42. Summary
• SPN by definition is 3 cm or less
▫ 40% are malignant
• REVIEW PRIOR FILMS!!!
• margins of the lesion and the presence or
absence of calcification should be assessed
• Lesions that are unchanged in size over a 2-year
period may be presumed to be benign and
followed up at 6-monthly intervals for a further
2 years.

43. • No change in 2 years…no further work-up
• The presence of central or ringlike calcification also
places the lesion in the benign category
• Working up SPN

44. THANK YOU