Pulmonary nodules (PNs) 1 cm or smaller have been detected on CT in lung cancer screening or the staging of lung cancer. Most of these nodules are benign but a few are malignant. Although the size criteria are used in managing them, the biopsy or repeated follow-up CT examinations may be uncomfortable for patients with benign PNs. The purpose is to clarify typical and atypical HRCT findings of benign PNs.
Two radiologists reviewed CT images of patients with one or two PNs 1cm or smaller, including 285 benign and 55 malignant nodules. The benign nodules were defined as a nodule pathologically diagnosed, shrinking or disappearing in follow-up studies or with no interval change for more than two years. Evaluated HRCT findings were size, shape, notch, satellite lesions, the relation to pleura and lobules, and so on. The frequencies of individual findings were compared between benign and malignant PNs.
HRCT findings with a high frequency and a positive predictive value (PPV) for a benign nodule were nodules, smaller than 5mm, of polygonal shape, and accompanied with satellite lesions or thickening of the bronchovascular bundle. The findings with a low frequency but a high PPV were a nodule of flat shape and with no relation to vessels. The findings with a high frequency but a low PPV were well-defined and smooth borders, and round or oval shape. The findings with a low frequency and a low PPV were irregular shape, density of GGA alone, notch, and spiculation.
A polygonal or semicircular nodule broadly contacted with the pleura and an intrapulmonary nodule with satellite lesions were typical HRCT findings of a benign nodule. Irregular nodules with notch on HRCT were, irrespective of the size, atypical for a benign PN.
To cure lung cancer patients, it may be clinically important to manage the patients with PNs 1 cm or smaller based on typical and atypical findings for benign PNs on HRCT.
T. Matsumoto, None.