solitary pulmonary nodule; pulmonary coin lesion

Introduction

A single rounded density seen on radiographs, 1-5 cm in diameter (> 4-6 mm, < 3 cm), located in lung parenchyma, usually well circumscribed, without satellite lesions.

A larger density is considered a pulmonary mass.

Etiology

• common
  • granuloma - tuberculosis, coccidioidomycosis, histoplasmosis, cryptococcosis
  • hamartoma of the lung
  • primary lung carcinoma,
    • bronchogenic carcinoma (35%)
    • lung adenocarcinoma tends to be peripheral
  • solitary metastasis to the lung
  • resolving pneumonia
• uncommon
  • carcinoid
  • bronchogenic cyst
  • resolving infarction
  • rheumatoid nodule
  • vasculitic nodule
  • arteriovenous malformation

History

• age, smoking, previous malignancy, exposure to tuberculosis, travel, recent respiratory tract infection, recent pulmonary infarction, recent trauma to chest, asthma, ENT symptoms, use of mineral oil or oily nose drops, immune status, CHF, connective tissue disease, family history (AV malformation)

Laboratory

• complete blood count (CBC)
• comprehensive chemistry profile
• rheumatology workup
  • erythrocyte sedimentation rate (ESR)
  • serum C-reactive protein
  • rheumatoid factor (if indicated)
  • reflex anti-nuclear antibody (ANA) panel (if indicated)
  • serum complement (if indicated)

Diagnostic procedures

• bronchoscopy
  • 60% diagnostic yield in lung cancer
  • provides sufficient information in 30% of cases
• transthoracic needle biopsy
  • CT or fluoroscopic guided
  • 85% diagnostic yield for lung cancer
  • 20% risk of pneumothorax
• a non-specific negative result does not exclude malignancy
• see lung carcinoma for suspected lung cancer
  • needle aspiration of suspicious peripheral lymph node

Radiology

• previous chest X-ray
• computed tomography (CT)
  • contrast enhancement suggests malignancy
  • spiculated borders suggests malignancy
  • helpful for assessing calcification
    • central calcification suggests granuloma
    • off-center calcification may be benign or malignant
    • calcification in rings or arcs suggests benign disease
    • diffuse calcification suggests benign disease
  • smooth borders suggests granuloma
  • subsolid or ground-glass nodules through which normal parenchymal structures are visible are often slow-growing adenocarcinomas
  • useful for staging of lung cancer
• PET scan
  • may be falsely negative with alveolar cell carcinoma
  • may be falsely positive with inflammation
• compare current with previous imaging prior to additional testing

* see Fleisher criteria for imaging of solitary pulmonary nodule

Complications

• more intensive diagnostic evaluation associated with greater procedural complications, radiation exposure, & costs

Management

• if > 8 mm, assess risk factors for lung cancer
• if nodule remains unchanged for 2 years, no follow-up is necessary, unless nodule is ground-glass appearing
  • such nodules may represent slow-growing lung adenocarcinoma
  • follow-up recommended for at least 5 years
• for current smokers with nodules <6 mm in size, follow-up CT at 12 months
  • if nodule is unchanged at 12 month, no further imaging is necessary
• for smokers with nodules 6-8 mm, CT at 6-12 months
• for non-smokers with nodules 6-8 mm, CT at 6-12 months
• for non-smokers & otherwise low-risk with nodules <6 mm, no follow-up needed
• for large solid nodules (>8 mm), follow-up at 3,9 & 12 months with contrast-enhanced CT, PET scan or lung biopsy
• a more complex algorithm
  • for small solid nodules (8 mm), follow Fleischner Society guidelines on intervals for repeat CT
  • for large solid nodules (>8 mm), assess the probability of malignancy according to clinical & imaging characteristics
  • further evaluation depends on whether calculated probability of malignancy is low (<5%), intermediate (5%-60%) or high (>60%) & is based partly on guidelines in
  • small pure subsolid nodule (5 mm) require no follow-up
• another algorithm
  • low or high risk
    • < 6 mm: no routine followup
    • 6-8 mm: CT at 6-12 months; then consider CT at 18-24 months
    • > 8 mm: CT at 3 months, PET/CT
• tissue diagnosis with lung biopsy or surgical resection if nodule is growing or exhibits high metabolic rate
  • referral to thoracic surgery for resection preferable to bronchoscopy
  • navigational bronchoscopy with better yield than conventional bronchoscopy
  • transthoracic fine-needle aspiration inadequate
• indications for surgical removal of nodule
  • solitary nodule is probably malignant
    • large nodule > 3 cm = pulmonary mass; >= 2.3 cm
    • spiculated nodule
  • lack of evidence to support benign nature of nodule
  • consider PET imaging for staging prior to surgical resection
• patient refuses surgery or is poor surgical risk
  • repeat chest X-ray every 3 months
  • enlargement of nodule may change patient's or surgeon's decision regarding surgery
• lesion most likely benign:
  • if there is not change in the size or shape of the nodule for over 2 years, repeat chest X-ray every 6-12 months
  • 35% of pulmonary nodules 8-20 mm surgically excised are benign

Factors favoring benign etiology

• age < 35
• female sex (Brock University says female sex is a risk factor for malignancy)
• non-smoker
• asymptomatic
• exposure to tuberculosis
• recent travel to region endemic for mycosis
• nodule size < 2 cm
• nodule present for more than 2 years (absence of enlargement for > 2 years)*
• doubling time of nodule < 30 days
• smooth nodule margins
• calcification, especially dense central calcification*
• satellite lesions present
• no enhancement on CT with contrast

* only reliable markers of benign nature

More general terms

• pulmonary nodule

Additional terms

• Fleisher criteria for imaging of solitary pulmonary nodule; Fleischner Society guidelines