JC13 (Surgery) - CXR Flashcards
Define size cut-off for lung mass
<3cm = nodule >3cm = mass
One nodule in one location = solitary pulmonary nodule (SPN)
Investigations for solitary pulmonary nodule (SPN)
Refer to previous CXR
1) SPN present in previous CXR:
- No growth over 2 year = likely Benign
- Interval growth = suspect malignant, proceed to CT scan
2) SPN not present in previous CXR:
- CT scan
- Bronchoscopy
- Sputum analysis
Imaging features of benign lung nodules
Benign: Round shape, well-circumscribed, smooth margin, uniform/ central calcification, Fat-containing, Minimal enhancement
Ddx infective cavitating lesion in lung (5)
Infections:
- Pulmonary Abscess: intermediate to thick wall, peripheral contrast enhancement, necrotizing center, +/- fluid level
- Septic Emboli (pathogens cause thrombosis in peripheral pulmonary capillaries): multiple peripheral nodular or wedge-shaped opacities with a broad base against the pleura
- Mycobacterium tuberculosis infection: upper lobe cavitary disease (immunocompetent) or lower lung zone disease, adenopathy, and pleural effusions (immunocompromised/ children)
- Non-tuberculous Mycobacterial (NTMB) Infection (e.g. M. avium-intracelluare and M. kansaii): similar upper zone TB but no hemoptysis
- Aspergillosis/ Aspergillus fumigatus: ground glass halo, fungal ball lesions that appear cavitary, crescent-shape air collection
CT Lung:
- Types
- Section width
- Function
Volumetric/ Helical/Spiral CT scan
- Used with IV contrast to enhance nodule characteristics
- Timing of IV contrast is determined by different pathologies (e.g. timing to contrast for PE is different from lung cancer
- Used for examining lung mass (no section width that can miss lesions)
High resolution CT scan
- No contrast used
- Used for interstitial lung disease
- 1-2mm slices taken 10mm apart
Use Hounsfield units to define nodule malignancy in contrast CT thorax.
Contrast CT:
- Nodule enhanced:
a) >25HU = malignant
b) Between 15 and 25 HU = Indeterminate
c) <15HU = Benign - Nodule not enhanced: Benign
Imaging features of malignant lung nodules
Malignant: Lobulated shape, spiculated margins (due to rapid growth) eccentric/ speckled calcification Pleural retraction Marked enhancement Heterogeneous
An solitary lung nodule has enhancement of 20HU in contrast CT. Is this malignant or benign?
Indeterminate
- Nodule enhanced:
a) >25HU = malignant
b) Between 15 and 25 HU = Indeterminate
c) <15HU = Benign
Plan of action after finding indeterminate nodule in lung
Close follow-up with CXR/ CT (3-6 months)
Percutaneous or transbronchial biopsy/ Resection to find cause
Investigations for suspected lung carcinoma
Contrast CT scan: TNM staging +/- biopsy at thorax and upper abdomen
Bronchoscopy: biopsy + BAL
Post-bronchoscopy sputum analysis
Name of lung tumor that is associated with upper limb motor deficit?
Structures that may be invaded?
Pancoast tumor
brachial plexus
Erosion of rib and left transverse process
soft tissue of back
3 uses of CT in management of lung cancer?
1) Staging, determine operability
2) Radiation planning, find disease extent, location and limit collateral damage
3) Re-evaluate treatment response
Limitation of contrast CT in examining mediastinal LN
Hard to assess:
Size
Cause of LN enlargement (inflammation or metastasis?)
Microscopic metastasis
Indeterminate chest wall or mediastinal invasion
List 5 ancillary investigations for lung cancer
Flexible bronchoscopy
Mediastinoscopy + biopsy
Transesophageal USG + biopsy
Thoracotomy + nodal sampling
PET scan (18-FDG)
Biopsy techniques for proximal vs peripheral lung lesions
Proximal lesion (close to hilum):
- Saline washing and brushing for microscopy and cytology
- Biopsy under direct vision for histology
Peripheral lesion: not visualized directly
- BAL for microscopy and cytology
- Transbronchial biopsy for histology
