SPN risk of malignancy
Info
Age (years)
Cigarrette smoking status Never smoked Current or former smoker
History of extrathoracic cancer diagnosed >5 years ago? Yes No
Diameter of SPN on CXR (mm)
Spiculation of SPN? Yes No
SPN in an upper lobe? Yes No
R e s u l t s
Probability of SPN being malignant (%)
? ? ?
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Info
SPN risk of malignancy

This clinical prediction model for assisting in the evaluation of Solitary Pulmonary Nodules (SPN's) was developed based upon a random sample of 419 patients and then tested on a separate group of 210 patients. In this group, 65% of nodules were benign, 23% were malignant and 12% were indeterminate.

Notes:

  • SPNs were 4-30 mm on CXR
  • Patients with any diagnosis of malignancy in the prior 5 years were excluded
  • Patients with any prior diagnosis of lung cancer were exlcuded

SPN's caused by:

  • Lung cancer
  • Metastatic lesion
  • Granuloma (~55%)
  • Hamartoma
  • Carcinoid tumor
  • Benign tumors

3 Clinical and 3 Radiographic findings were found useful in prediction of whether a given SPN was malignant:

  • Clinical:
    • Age
    • Cigarette smoking status
    • History of cancer >=5 years ago
  • Radiographic:
    • Diameter
    • Spiculation
    • Upper lobe location

Probability of Malignancy = e x (1+e x )

X is the sum of the following:

  • -6.8272 (a constant)
  • +0.0391 × age in years
  • +0.7917 (if current or former smoker)
  • +1.338 (if diagnosed with extrathoracic cancer >5 years ago)
  • +0.1274 × diameter of SPN in mm
  • +1.0407 (if the SPN has spicules)
  • +0.7838 (if the SPN is located in an upper lobe)

Reference:

Swensen SJ, Silverstein MD, Ilstrup DM, et al. The probability of malignancy in solitary pulmonary nodules. Application to small radiologically indeterminate nodules. Arch Intern Med. 1997;157(8):849-55.