CT scans.—A micronodule is a discrete, small, round, focal opacity. A variety of diameters have been used in the past to define a micronodule; for example, a diameter of no greater than 7 mm (86). Use of the term is most often limited to nodules with a diameter of less than 5 mm (87) or less than 3 mm (88). It is recommended that the term be reserved for opacities less than 3 mm in diameter. (See also nodule, miliary pattern.) [Fleischner Society]
In the lung, a micronodule is defined as a nodule less than 3mm in size.