"Early" peripheral lung cancer: Prognostic significance of ground glass opacity on thin-section computed tomographic scan

Background. The number of peripherally located lung cancers with an excellent prognosis has been increasing, possibly due to the introduction of computed tomography for lung cancer screening in Japan. The concept of peripherally located "early lung cancer" remains controversial. Methods. A retrospective study was conducted on 1,540 lung cancers resected at our institute between May 1992 and December 2000. The sizes of solid attenuation and ground glass opacity were evaluated radiologically and the relationships between radiologic findings and clinicopathologic features were investigated to define peripheral early lung cancer. Results. Sixty-nine (4.4%) lung cancers showed a large ground glass opacity component on thin-section computed tomographic scan. The maximum tumor dimension ranged from 6 to 41 mm, and all tumors were clinical stage I. Forty-seven patients were diagnosed as having bronchioloalveolar carcinoma pathologically. None of the tumors showed lymph node involvement or lymphatic invasion. Only two showed vascular invasion, but all were pathologic stage I disease. Most of the lung cancers that showed pure ground glass opacity were bronchioloalveolar carcinoma. Conclusions. Peripheral lung nodules with a large ground glass opacity component on thin-section computed tomographic scan, which do not disappear during follow-up, tend to be bronchioloalveolar carcinomas or minimally invasive adenocarcinomas of the lung. These findings warrant a feasibility study of limited surgical resection for such lung tumors.