Study objective: To reevaluate whether it is possible to reliably differentiate malignant mediastinal lymph nodes from benign nodes by size, and to determine the frequency of metastases to normalsized mediastinal lymph nodes that directly affects the sensitivity for detecting malignant mediastinal lymph nodes (N2 nodes) on CT.
Design: Prospective study of patients with non-small cell lung cancer.
Setting: Department of Radiology and First Department of Surgery, Yamaguchi University School of Medicine.
Patients: We examined 40 patients with non-small cell lung cancer, who underwent thoracotomy because of operable stage (stage I, II, IIIA) in preoperative staging, using CT and transesophageal echocardiography (TEE).
Measurements and results: Lymph nodes 10 mm or greater in short-axis diameter on CT and TEE were considered abnormal. Furthermore, lymph node size was measured by TEE and nodal specimens in long- and short-axis diameter in each patient. Two hundred eight mediastinal lymph nodes were dissected and N2 nodes were present in 28% of patients (11/40); in 7 of these 11 patients (64%), mediastinal lymph node metastases were misdiagnosed on CT because of normal-sized N2 nodes. Furthermore, in 73% of N2 nodes, nodal size was normal on TEE. There were no significant difference in both diameters between malignant mediastinal lymph nodes and benign nodes on TEE and nodal specimens.
Conclusions: It is not possible to reliably differentiate malignant mediastinal nodes from benign nodes by size alone, and we should be aware of high frequency of normal-sized N2 nodes in patients with operable stage of lung cancer.
Worldwide, lung cancer is a common cause of death in both men and women. Accurate staging of lung cancer, assessing the extent of local and distant disease, is necessary to determine resectability and overall prognosis. CT enables noninvasive preoperative assessment of mediastinal lymph nodes in lung cancer. Although most early articles reported high sensitivity for detecting nodal metastases, more re-cendy published articles have suggested that CT has a low sensitivity. CT data are based on analysis of the size of lymph nodes and depend on the belief that malignant lymph nodes will be larger than benign nodes, and that smaller lymph nodes are more likely to be benign. Furthermore, the frequency of metastases to normal-sized mediastinal lymph nodes is a subject of debate that direcdy affects the sensitivity of CT. Therefore, we reevaluate whether it is possible to reliably differentiate malignant mediastinal lymph nodes from benign lymph nodes by size using nodal specimens and transesophageal echocardiography (TEE), and determine the frequency of metastases to normalsized mediastinal lymph nodes in patients with nonsmall cell lung cancer.