[Benign pulmonary nodule: morphological features and contrast enhancement evaluated with contiguous thin-section CT].

The morphological changes in 54 benign lung nodules, including 8 histologically proven nodules of tuberculoma, 10 of focal organizing pneumonia (FOP), 1 of lung abscess and 35 other benign nodules, were evaluated with contiguous thin-section (3mm) CT. In addition, incremental dynamic studies were carried out in 25 of these nodules. The three-dimensional shapes of the nodules were found to be quite varied and were classified into four types: (A) round mass (n = 18), (B) polygonal mass with concave or straight margins (n = 20), (C) oval or band-like mass extending along the bronchovascular bundle (n = 7), (D) oval mass attached to the pleura with broad contact (n = 9). Forty-two (78%) of the 54 nodules were located along the bronchovascular bundle. The maximum increments in CT values over 20HU were observed after contrast enhancement in 18 (72%) of the 25 benign nodules, among which all tuberculomas showed little or no contrast enhancement. The number of small vessels quantified microscopically in teh center of the nodules were minimal in tuberculomas with little enhancement and plentiful in lesions of FOP and abscess which showed marked enhancement. Our results suggest that the differentiation between benign and malignant pulmonary nodules is not possible simply on the basis of the degree of contrast enhancement. Therefore, morphological features and the anatomical relation to the bronchovascular bundles should also be taken into consideration in the diagnosis of pulmonary nodules.