A 55-year-old smoker has a 2 cm spiculated pulmonary nodule on CT. PET-CT shows SUVmax of 8.2 in the nodule. Which additional CT finding would MOST favour primary lung adenocarcinoma over a metastasis from a colon primary?

• A Well-defined smooth border with no spiculation
• B Central calcification in a popcorn pattern
• C Pleural tags and vascular convergence ✓
• D Multiple similar nodules in both lungs

Explanation

Pleural tags (linear strands extending to the visceral pleura) and vascular convergence (vessels appearing to converge toward the nodule) are characteristic CT signs of primary lung carcinoma, particularly adenocarcinoma, reflecting desmoplastic reaction and local invasion. A smooth, well-defined border is more typical of a metastasis. Popcorn calcification indicates a hamartoma. Multiple bilateral nodules suggest haematogenous metastases.

Reference: Grainger & Allison's Diagnostic Radiology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.