Purpose: We retrospectively reviewed a series of proven lung metastasis to evaluate the frequency and CT features of metastases showing an air-space (lepidic) pattern of growth.
Method: CT examinations of 65 patients with proven lung metastasis from GI carcinomas were reviewed by three observers. Four CT features were used to classify lesions as air-space metastases: (a) air-space nodules; (b) parenchymal consolidation containing air bronchogram and/or showing angiogram sign; (c) focal or extensive ground-glass opacities; and (d) nodules(s) with a "halo" sign.
Results: Six of 65 patients showed air-space metastases: three from pancreatic carcinoma, two from colonic carcinoma, and one from jejunal carcinoma. In one case, metastasis appeared as extensive parenchymal consolidation associated with ground-glass opacities; in one as an area of ground-glass opacity; in one as an extensive parenchymal consolidation with air bronchogram; in one as parenchymal consolidations with angiogram sign and multiple nodules, some of these with halo sign; in one as air-space nodules and patchy air-space consolidations; and in one as a solitary nodule with halo sign.
Conclusion: Our study shows that air-space lung metastasis from GI carcinomas is uncommon but not rare. On CT as well as microscopically, differential diagnosis between air-space metastasis and bronchioloalveolar carcinoma may be impossible.