CT- and computer-based features of small hamartomas

To identify characteristic computed tomographic (CT) and computer-derived features of hamartomas manifesting as small pulmonary nodules.

Individuals with a diagnosis of hamartoma were identified among participants in the International Early Lung Cancer Action Program and were included if there thin section CT images that included the entire nodule. The CT findings were reviewed to determine the nodule consistency (solid, part-solid, nonsolid), nodule diameter (average of length and width), shape (round, lobulated, neither) and edge (smooth, not smooth). Computer measures of nodule compactness, sphericity, surface regularity and gradient (change in gray-scale between the nodule and the surrounding parenchyma) were determined. Volume doubling time (VDT) was also determined for those with at least two scans with similar imaging acquisitions.

A total of 21 cases of hamartomas that had histologic or cytologic confirmation were identified. The median age was 60 and 12 (57%) were men. Average diameter was 10.7 mm (5-20.7 mm). All were solid in consistency and were described by the radiologist as having either round or lobulated shape with a smooth edge. None had pathognomonic radiologic findings for hamartoma. Computer measures demonstrated that all were compact and spherical, with a regular surface and a sharp margin between the nodule and surrounding parenchyma. Of nine on whom the VDT could be calculated, eight had VDTs longer than 450 days.

Both radiologist and computer derived features of small hamartomas suggest a consistent presentation for these lesions which may be helpful in distinguishing them from other types of nodules.