Pure ground-glass and part-solid nodules follow their own Fleischner rules; the solid component size (on lung window, in mm) decides the category, and slow growth over years is the rule rather than the exception.
Orient first
- Spectrum: atypical adenomatous hyperplasia → adenocarcinoma in situ → minimally invasive → invasive adenocarcinoma.
- Transient subsolid nodules (infection) resolve at 3 months — the first follow-up confirms persistence.
- The solid component measured on lung window correlates with invasive size.
Acquire the study
- Thin-section (≤ 1 mm) non-contrast CT chest; volumetry where available; same technique on follow-up.
The manoeuvre
- Lung window: classify — pure ground-glass vs part-solid; average diameter in mm (mean of long and short axes).
- Part-solid: solid component size in mm on lung window.
- Features raising concern: bubble lucency, spiculation, pleural retraction, growth of the solid part.
- Compare with all prior CTs over the interval; apply the Fleischner (incidental) or Lung-RADS (screening) category (use the calculator).
What confirms it
- A persistent part-solid nodule with a growing solid component is presumed invasive adenocarcinoma.
What licenses you to exclude it
- Resolution on 3-month follow-up means it was transient.
The classic misread
- Measuring the solid component on mediastinal window, or comparing only with the last scan.