The ratio of the maximum high attenuation area dimension to the maximum tumor dimension may be an index of the presence of lymph node metastasis in lung adenocarcinomas 3 cm or smaller on high-resolution computed tomography

Background: Limited resection of the lung can improve the postoperative quality of life if there is no lymph node metastasis. Small adenocarcinomas frequently appear on radiographs with areas of ground glass attenuation. We examined whether there is a correlation between the presence of lymph node metastasis and the ratio of the intratumor high-attenuation area (greatest dimension of high-attenuation area [H] to the maximum tumor dimension [T], H/T ratio) on high-resolution computed tomography (HRCT). Methods: From January 1996 to June 2004, we studied 281 patients with lung adenocarcinomas of 3 cm or less in maximum dimension on preoperative HRCT. Each of the 281 patients had a lobectomy and lymph node dissection, and there was no case of limited resection. Results: Lymph node metastasis was present in 11.4% (32 of 281 cases, N1 = 13 cases, N2 = 19 cases). None of the 94 cases with an H/T ratio of 60% or less had lymph node metastasis. Moreover, lymph node metastasis was noted even in a 6-mm tumor when the H/T ratio was 100%. Of the 187 cases with tumors having an H/T ratio greater than 60%, 32 had lymph node metastasis. Conclusions: The relationship between the H/T ratio and lymph node metastases was evaluated by HRCT in lung adenocarcinomas 3 cm or smaller in maximum dimension. The H/T ratio may provide useful information in deciding on limited resection for lung cancer in such cases.