Solitary Pulmonary Nodule
The incidental lung finding that demands systematic evaluation — from imaging characteristics to VATS excision.
A single, round, discrete pulmonary opacity measuring <3 cm in diameter, surrounded by normal lung tissue, and not associated with lymphadenopathy or atelectasis. Focal lesions >3 cm are termed lung masses and should be considered malignant until proven otherwise.
Aetiology
| Category | Causes |
|---|---|
| Congenital | Bronchogenic cyst, sequestration, bronchial atresia |
| Infections | Infectious granuloma, histoplasmosis, organising pneumonia, rounded atelectasis, parasitic lesions |
| Inflammatory | Sarcoidosis, rheumatoid arthritis, Wegener's granulomatosis, lymphadenopathy |
| Vascular | Lung infarct, AV malformation |
| Benign neoplasia | Hamartoma, chondroma, fibroma, lipoma, leiomyoma, teratoma |
| Malignant neoplasia | Primary lung cancer, solitary metastasis (breast, head and neck, melanoma, colon, kidney, sarcoma), carcinoid |
| Miscellaneous | Mucus plug, amyloidosis, artefacts (nipple shadow, chest wall swelling) |
Over 90% of SPNs are diagnosed incidentally on routine screening. Most patients are asymptomatic. The primary clinical task is to risk-stratify for malignancy and determine the need for tissue diagnosis or surveillance.
Risk factors for malignancy
- Age >60 years
- Smoking history
- Previous or associated malignancy
- History of COPD, pulmonary fibrosis, or prior TB/fungal infection
- Occupational exposure to asbestos
- Family history of lung cancer
Diagnostic workup
| Feature | Benign | Malignant |
|---|---|---|
| Margins | Smooth, rounded, scalloped | Spiculated, corona radiata sign |
| Calcification | >50% calcified; laminated, central, or diffuse pattern; popcorn (hamartoma) | <15% calcified; stippled or eccentric pattern |
| Enhancement (CT contrast) | <15 HU | >15–20 HU |
| Doubling time | Stable >2 years = almost certainly benign | Doubling time 30–465 days |
| Other features | Fat attenuation (hamartoma) | Sub-solid (ground glass or part-solid), air bronchogram, pseudocavitation, thick-walled cavity (>15 mm) |
Investigation modalities
- CT chest: characterises the nodule — size, margins, attenuation, calcification pattern, doubling time on serial imaging
- PET-CT: SUV >2.5 associated with >90% probability of malignancy for nodules >10 mm; sensitivity and specificity fall for smaller lesions
- Bronchoscopy: for central airway lesions; diagnostic yield 10–50% for nodules <2 cm with fluoroscopic guidance
- CT-guided TTNA: most useful for peripheral lesions in the outer third of the lung; sensitivity depends on nodule size, needle calibre, and on-site cytopathology
- VATS wedge excision: for peripheral SPNs with high probability of malignancy (>60%); sensitivity and specificity approach 100%; allows simultaneous diagnosis and definitive resection
Management principles
For peripheral SPNs with high malignancy probability, VATS wedge resection followed by intraoperative frozen section allows simultaneous diagnosis and definitive resection (lobectomy if malignant) at one sitting — cost-effective and clinically sound. Always confirm the nodule is within reach of VATS before proceeding — CT-guided wire localisation or hookwire placement may be needed for small peripheral nodules.
Management protocols for SPNs detected on CT screening (size thresholds, surveillance intervals) are regularly updated. Refer to the Fleischner Society guidelines (2017) and NCCN lung cancer screening guidelines for current recommendations.
All clinical content should be verified against current guidelines before clinical application. This resource is intended for revision and educational purposes only.
Standard textbooks
- Shields TW, LoCicero J, Reed CE, Feins RH. General Thoracic Surgery. 7th ed. Lippincott Williams & Wilkins.
- Sellke FW, del Nido PJ, Swanson SJ. Sabiston & Spencer Surgery of the Chest. 9th ed. Elsevier.
- Pearson FG, et al. Thoracic Surgery. 3rd ed. Churchill Livingstone.