The basis and mechanisms of enhancement of solitary pulmonary nodules (SPNs) were studied by comparison with the microvessel density and basement membrane of microvessels.

Dynamic contrast enhancement CT scannings were undergone on 38 cases of peripheral lung cancer, 5 cases of harmatoma and 10 cases of inflammatory lesions which less than 3cm . The microvessel density (MVD) and the basement membrane of microvessels of the resected specimens were labeled using the ABC immuno-histochemical method in all patients. The CT values and MVDs in different groups were compared by student-test, the correlations between CT enhancement and MVDs were analyzed using the Spearman correlation coefficient(r value), while X2-test was used among the different groups for basement membrane of microvessels, and a P value of less than 0.05 was considered statistically significant.

The enhancement of lung cancer and inflammatory lesions were significantly higher than that of harmatoma ,while the time-attenuation curve of inflammatory lesions tended to increase faster and reach a higher peak value than lung cancer, both of them maintained a high plateau after crossing. The harmatoma showed limited increase and demonstrating a low plateau curve.
The MVD of SPNs correlated positively with CT enhancement(r=0.8051), the microvessel counts of peripheral lung cancer and inflammatory lesions were significantly higher than that of harmatoma(48.45±10.09Hu and 49.60±19.94Hu Vs 8.70±7.30, t=11.64,t=6.09,p<0.001), but the lung cancer could not be differentiated from the inflammatory lesions(t=-0.26,p=0.799>0.05).
There were not any differences in the continuities of basement membrane between nodules which enhanced less than 30Hu and higher than 30Hu(X2=3.13,p>0.05).

The MVDs mainly contributed to the enhancement of SPNs, the basement membrane hadn’t the relationship with nodule enhancement, but might influence the pattern of time-attenuation curve.