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.