A

B

C

SHAPE - round

MARGIN - smooth

SIZE - 1-2 mm

DENSITY - can't tell on these CT windows (lung windows)

NOTE: any round lung opacity that is less than 3 cm in diameter can be called a 'NODULE'

SHAPE - irregular

MARGIN - spiculated

SIZE - 4 cm

DENSITY - can't tell on these CT windows (lung windows)

NOTE: any lung opacity that is over 3 cm in diameter or spiculated in shape must be called a 'MASS'

SHAPE - round

MARGIN - smooth

SIZE - 2.5 cm

DENSITY - contains central calcification, clearly seen on these windows (soft tissue)

NOTE: any round lung opacity that is less than 3 cm in diameter should be called a 'NODULE' - some patterns of calcification, like this, indicate a BENIGN etiology