Table 1.

Nodule categorization based on size and characteristics (new nodules) and growth rate (existing nodules) in NELSON study

Category	Definition
NODCAT 1	A benign nodule (with fat/benign calcifications) or other benign abnormalities
NODCAT 2	A nodule, smaller than NODCAT3, not belonging to NODCAT1
	Solid	Partial solid	Non-solid
NODCAT 3	50 ≤ V ≤ 500 mm3	Solid component: 50 ≤ V ≤ 500 mm3	dmean ≥ 8 mm
	Pleural based: 5 ≤ dmin ≤ 10 mm	Non-solid component: dmean ≥ 8 mm
NODCAT 4	V > 500 mm3	Solid component: V > 500 mm3	Non-existent category
	Pleural based: dmin > 10 mm
GROWCAT A	VDT > 600 days
GROWCAT B	400 ≤ VDT ≤ 600 days
GROWCAT C	VDT < 400 days, or new solid component in non-solid lesion

V, volume; d_min, minimal diameter; d_mean, mean diameter; VDT, volume-doubling time.