Clinicopathological Features of Small-sized Non-small Cell Lung Cancer with Mediastinal Lymph Node Metastasis

Introduction: In clinical practice, peripheral small-sized lung cancers with positive mediastinal lymph nodes are sometimes detected. To understand the characteristics of these aggressive tumors, we reviewed the clinicopathological features of small-sized non-small cell lung cancer patients with mediastinal lymph node metastasis resected in our institution.

Methods: We studied 360 patients with small-sized lung lesions with a maximum diameter of 2 cm or less. The clinicopathological characteristics of each patient were reviewed and compared among the subgroups, which were stratified according to pathological nodal status.

Results: 21 patients (5.8%) had a positive mediastinal lymph node. Among them, 17 patients had lung lesions larger than 1.5 cm. No mediastinal nodal involvement was found in patients with squamous cell carcinomas. In contrast, mediastinal nodal involvement was significantly common in patients with poorly differentiated carcinoma (P=0.004) and high serum carcinoembryonic antigen levels detected during preoperative evaluation (P=0.006). None of the 14 patients with upper lobe tumor had a positive subcarinal lymph node. Lower lobe tumors frequently developed extensive multiple-level involvement, which included the upper mediastinum. Radiographic evaluation of pN2 patients using computed tomography revealed a total absence of ground-glass opacity, or the presence of a small area of ground-glass opacity.

Conclusions: Most small-sized non-small cell lung cancer cases with mediastinal lymph node metastasis were invasive adenocarcinoma with poor differentiation, which usually showed a solid shadow without ground-glass opacity on computed tomography.