Is it possible to differentiate malignant mediastinal nodes from benign nodes by size? Reevaluation by CT, transesophageal echocardiography, and nodal specimen.

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 normal-sized 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).

INTERVENTIONS

None.

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.