Pulmonary nodules are small, rounded opacities measuring within the pulmonary interstitium. According to some publications thay can measure up to 30 mm reference required. They are generally homogenous (without air bronchograms or alveolograms) and are well-defined since their margins are sharp and they are surrounded by normal aerated lung. They are quite separate from airspace nodules that often have an irregular margin and are usually approximately 8 mm in diameter. (For further discussion, see the article on nodular opacification.)
Another common methods of classifying pulmonary nodules is as
According to morphology
- solid pulmonary nodules
- partly solid pulmonary nodules
- ground glass pulmonary nodules
According to distribution (if multiple)
Pulmonary nodules are common and, as the spacial resolution of CT scanners has increased, detection of smaller and smaller nodules has occured. Miliary nodules are tiny modular opacities that measure less than 2 mm. Some authorities make a distinction between a micronodule (2-7 mm) and a nodule (7-30 mm). Most sources agree that where a nodule is larger than 30 mm, it is termed a pulmonary mass.
A micronodular or miliary pattern is predominatly seen in granulomatous processes, haematogenous metastases to the lungs and pneumoconioses. Nodules and masses are most often seen in metastatic disease to the lung.