Radiologic classification of small adenocarcinoma of the lung: Radiologic-pathologic correlation and its prognostic impact

Background. A new radiologic classification for small adenocarcinoma is necessary for discussions of limited surgical resection for peripheral lung cancer. Methods. Between 1999 and 2003, 1,697 consecutive patients underwent pulmonary resection for lung cancer. Three hundred forty-nine of these patients with clinical stage IA lung cancer who had lung peripheral adenocarcinoma, 2 cm or less in size, were investigated retrospectively. Radiologic classification was based on the findings of thin-section computed tomographic scan such as the presence of solid and ground-glass opacity (GGO). Type 1 (n = 22), type 2 (n = 26), type 3 (n = 25), and type 4 (n = 43) show a simple GGO, an intermediate homogeneous increase in density, a halo, and a mixed area of GGO and a solid, respectively. Type 5 (n = 54) shows a solid tumor with GGO, and type 6 (n = 179) shows a solid tumor. Results. There was no difference in the maximum tumor dimension among the six groups. All but 1 patient had no lymph node metastases among type 1 to 4 tumors, whereas these were found in 5% and 24% of the patients with type 5 and 6 tumors, respectively. Lymphatic invasions were rarely found in patients with type 1 to 4 tumors (p < 0.001). Conclusions. Types 1, 2, 3, and 4 are considered to be radiologic early adenocarcinoma of the lung, and their pathologic features were minimally invasive. On the other hand, type 5 and 6 tumors could have lymph node metastases and are considered to be invasive adenocarcinoma. Although limited surgical resection may be enough for type 1 to 4 tumors, anatomic pulmonary resection should be recommended for type 5 or 6 tumor.