Lung Nodule

1. Definition
   1. Solitary Lung Nodule
      1. Isolated spherical opacity on xray <3 cm in diameter
2. Epidemiology
   1. Incidence
      1. Chest XRay: 0.2% of all Chest XRays
      2. CT Chest: 13-15% of all scans
3. Background
   1. Obtain CT Chest to further evaluate Lung Mass identified on Chest XRay
   2. Evaluation below is based on the CT Chest
   3. Compare findings to prior imaging (critical!)
4. Differential Diagnosis
   1. Benign
      1. Lung Hamartoma (15%)
      2. Nonspecific Granuloma (15%)
      3. Infectious Granuloma (15%)
         1. Aspergillosis
         2. Coccidioidomycosis
         3. Cryptococcosis
         4. Histoplasmosis
         5. Tuberculosis
   2. Malignant
      1. Lung Adenocarcinoma (47%)
      2. LungSquamous Cell Carcinoma (22%)
      3. Metastasis (8%)
      4. Lung Non-small cell carcinoma (7%)
      5. Lung small cell carcinoma (4%)
5. Imaging: Modalities
   1. Chest XRay (PA and lateral)
      1. Nodules at 5 mm may be visualized
      2. Poor Test Sensitivity (high false negative rate)
      3. Nodules often noted as incidental XRay finding
   2. CT Chest (thin slice)
      1. Greater Test Sensitivity and Test Specificity than Chest XRay
      2. CT is a first-line test in evaluation of Solitary Lung Nodules found on Chest XRay
   3. FDG-PET
      1. High Test Specificity and Test Sensitivity for Solitary Lung Nodules >8-10 mm
      2. Indicated when indeterminate findings persist on CT or findings discordant with estimated cancer risk
   4. MRI Chest
      1. Not recommended in evaluation of Solitary Lung Nodule
6. Imaging: Red flag findings on CT Chest (suggestive of malignancy)
   1. Non-calcified or eccentric calcification
   2. Nodule size >10 mm
      1. Contrast with benign lesions which are typically <5 mm in size
   3. Irregular or spiculated border
      1. Contrast with benign lesions which have a smooth border
   4. Non-solid, ground-glass appearance
      1. Contrast with benign lesions that are dense and solid
   5. Doubling time between 1 month and 1 year
      1. Contrast with benign lesions that double in weeks or over years
7. Risk Factors: Lung Cancer (used below to distinguish low risk from high risk)
   1. Current or past Tobacco use
   2. Age over 40 years
   3. History of prior malignancy
   4. Spiculation
   5. Upper lobe location
      1. Swenson (1997) Arch Intern Med 157: 849-55
   6. Contrast enhancement
      1. Non-enhancing lesion has 97% Negative Predictive Value for cancer
      2. Swenson (2000) Radiology 214: 73-80
   7. Non-calcified lesion
      1. Calcification either centrally or completely suggests a benign lesion
   8. Semi-solid Nodules (63% malignant)
      1. Contrast with 18% malignancy with ground-glass lesions
      2. Contrast with 7% malignancy with solid lesions
      3. Henschke (2002) AJR 178: 1053-7
   9. Size (most important factor)
      1. Size<5 mm: Less than 1% malignancy risk
      2. Size 5-10 mm: 6-28% malignancy risk
      3. Size 11-20 mm: 33-60% malignancy risk
      4. Size 20-30 mm: 64-82% malignancy risk
      5. Wahidi (2007) Chest 132: 94-107
8. Evaluation: Nodule 8-30 mm
   1. General
      1. Discuss with pulmonology, thoracic surgery or radiology for work-up
      2. Cancer probability (used below) is calculated from VA Model or Mayo Model
      3. Consider starting preoperative evaluation while awaiting biopsy
         1. Pulmonary Function Tests
         2. Electrocardiogram and other cardiac testing as needed
         3. Optimize comorbid conditions
   2. Low probability of cancer (<5% chance of cancer)
      1. Repeat CT chest in 3, 6, 12 and 24 months
   3. Intermediate probablity of cancer (5-60% chance of cancer)
      1. CT chest with trans-thoracic fine needle aspirate (TTNA) or
         1. First choice due to high Specificity (97%) and high sensitivity (90%)
         2. Schreiber (2003) Chest 123:1155
      2. Fluorodeoxyglucose-Positron Emission Tomography (FDG-PET) or
      3. Bronchoscopy with biopsy
   4. High probability of cancer (>60% chance of cancer)
      1. Thoracoscopic surgery with frozen sections and possible resection
9. Evaluation: Nodule <8 mm
   1. Nodule 6-8 mm
      1. Low risk patient: Repeat CT chest in 6-12 months and 18-24 months
      2. High risk patient: Repeat CT chest in 3-6 months, 9-12 months and 24 months
   2. Nodule 4-6 mm
      1. Low risk patient: Repeat CT chest in 12 months
         1. If normal repeat CT, no further evaluation is needed
      2. High risk patient: Repeat CT chest in 6-12 months and 18-24 months
   3. Nodule <4 mm
      1. Low risk patient: No follow-up needed
      2. High risk patient: Repeat CT chest in 12 months
         1. If normal repeat CT, no further evaluation is needed
10. Resources
    1. Online calculator of Lung Cancer risk
       1. http://www.chest-xray.com/spn/spnprob.html
       2. Establishes pretest probability of cancer and helps drive evaluation based on patient risk
11. References
    1. Midthun (2011) Internal Medicine, Mayo Conference, Kauai
    2. Albert (2009) Am Fam Physician 80(8): 827-31
    3. Gould (2007) Chest 132(suppl 3):108S-130S
    4. MacMahon (2005) Radiology 237(2):395-400