Radiopathologic correlation of collision lung cancer with ground-glass opacity.

Pulmonary collision tumors have been described as a special entity of synchronous multiple lung cancer. There have been no reports detailing the chronological changes in primary collision lung cancers on chest computed tomography. We report a case of ground-glass lung nodules gradually colliding with each other. The collision tumors of the lung were composed of minimally invasive adenocarcinoma and adenocarcinoma in situ with epidermal growth factor mutations. Immunohistochemically, the Ki-67 labeling indices were different in the 2 components. Ki-67 staining was useful to distinguish the 2 components. The 2 dominant ground-glass tumors grew slowly with radiologic and pathologic heterogeneity.