Histogram analysis of computed tomography numbers of clinical T1 N0 M0 lung adenocarcinoma, with special reference to lymph node metastasis and tumor invasiveness

Purpose: To predict lymph node metastasis and tumor invasiveness in lung adenocarcinoma from computed tomography findings, we examined computed tomography number histograms of clinical T1 N0 M0 lung adenocarcinomas. Patients and Methods: Histograms of pixel computed tomography numbers were made for 100 patients with clinical T1 N0 M0 lung adenocarcinoma. Pathological tumor stages were N0 in 80 patients, N1 in 7, N2 in 9, and T4 due to intrapulmonary metastasis in 4. Results: The histogram showed 3 patterns: 1 peak at a low computed tomography number (n = 18), 1 peak at a high computed tomography number (n = 54), and 2 peaks at both low and high computed tomography numbers (n = 28). Histologically, adenocarcinoma with 1 peak at a low computed tomography number showed a large area of bronchioloalveolar carcinoma-like spread with little area of solid growing tumor or central fibrosis, whereas those with 1 peak at a high computed tomography number showed a large area of solid growing tumor or central fibrosis with little bronchioloalveolar carcinoma-like spread. Adenocarcinomas with 2 peaks had both types of areas. Lymph node or pulmonary metastases were seen in none (0%) of the adenocarcinomas with 1 peak at a low computed tomography number, in 1 (4%) with 2 peaks, and in 20 (37%) with 1 peak at a high computed tomography number. The former 2 types had metastases less frequently than those with 1 peak at a high computed tomography number (P < .01). In the 79 patients with pathological T1 N0 M0, tumor involvement of the intratumoral vessels or pleura was seen in 1 of 18 (6%) adenocarcinomas with 1 peak at a low computed tomography number, which was significantly less frequent than the 18 of 34 (53%) with 1 peak at a high computed tomography number (P < .001) and 10 of 27 (37%) with 2 peaks (P < .05). Conclusion: Clinical T1 N0 M0 adenocarcinomas with 1 peak at a low computed tomography number on histogram seldom had lymph node metastasis or tumor involvement of vessels or pleura. Limited surgical resection could be indicated for this type of adenocarcinoma, especially for elderly patients or patients with poor pulmonary function.