Objective: To determine the optimum selection of mediastinal lymph nodes for biopsy in non-small cell lung cancer (NSCLC), lymph nodes with or without metastasis at each mediastinal station were ranked in size in patients with pathological N2 disease.
Methods: Twenty-five NSCLC patients with pathological N2 disease who underwent pulmonary resection with complete mediastinal lymph node clearance were examined. Of 114 mediastinal lymph node stations dissected, 47 had metastases and 67 did not. The sizes of 259 nodes in the 47 positive lymph node stations were measured. Of these 259 nodes, 137 had metastases and 122 did not. The short- and long-axis diameters of the 259 lymph nodes were ranked in each lymph node station.
Results: Mean short- and long-axis diameters of lymph nodes with metastases were significantly greater than those without (p < 0.001). In 47 metastatic lymph node stations, the short- and long-axis diameters were greatest in a metastatic node in 44 (94%) and 42 (89%) respectively, whereas in the remaining 3 (6%) and 5 (11%), the second largest but not the largest node was positive. None of the largest lymph nodes with metastasis were smaller than the second largest lymph node at each station. Four of the 10 patients with adenocarcinoma (40%) had metastasis in the second largest but not in the largest node measured by long-axis diameter, a significant difference from one in eight (12.5%) among the squamous cell carcinoma cases (p = 0.04).
Conclusion: For mediastinal lymph node biopsy, both the largest and the second largest node at each station should be sampled, especially in adenocarcinoma. If only the largest lymph node is selected, false-negative results will occur at a rate of about 10%.