April 11, 2013

Solitary Pulmonary Nodule: Definition, DDx, and Evaluation with CT

Axial scan of the lung nodule in mediastinal window reveals a solid component of the nodule without calcification
Axial scan of the lung nodule in lung window shows a lobulated, smooth margin of the nodule

Definition of SPN

  • Radiographic opacity of equal to or less than 3 cm
  • At least two thirds of margins are surrounded by lung parenchyma
  • Exclusion of lymph nodes (not always possible), atelectasis and postobstructive pneumonia
Differential Diagnosis
  • Infectious: TB, pneumonia, abscess, fungus, etc
  • Neoplastic: benign and malignant
  • Vascular: AVM, infarct, aneurysm venous varix, hematoma
  • Congenital: bronchogenic cyst, sequestration, bronchial atresia
  • Inflammatory: rheumatoid arthritis, Wegener, sarcoidosis, microscopic angiitis
  • Lymphatic: lymph node, lymphoma
  • Outside the lungs: skin nodule, nipple shadows, rib fracture, pleural lesion
  • Miscellaneous: rounded atelectasis, lipoid pneumonia, amyloidosis, etc
CT Evaluation
  • Thin-section (1 mm) contiguous images through nodule are suggested
  • Both lung and mediastinal windows obtained (lung window for margins/edges, mediastinal window for solid component)
  • Low dose (less than 80 mAs) can be used for purpose of nodule characterization
CT Characteristics
  • Growth rate: malignancy likely if doubling time = 20-400 days
  • Size: malignancy likely if size > 3 cm
  • Margin/border/edge: malignancy likely if lobulated, speculated, ragged, halo, notches
  • Calcification: attenuation > 200 HU indicates presence of calcium in the nodule. No pattern of calcification specific for malignancy
  • Cavitation: malignancy likely if irregular and thick (> 15 mm) wall

Our case: Solitary pulmonary nodule from a metastatic colon cancer

Patel VK, Naik SK, Naidich DP, et al. A practical algorithm approach to the diagnosis and management of solitary pulmonary nodules. Part 1: radiologic characteristics and imaging modalities

1 comment:

Anonymous said...

Thanks for posting this. What kinds of tests is radiology done with. Should I be concerned at all about any inherent risks with it? I'm asking because my mother said she needs to speak to a radiologist in Dallas and that worries me.

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