Clinical significance of intranodal and extranodal growth in lymph node metastases of non-small cell lung cancer.

In non-small cell lung cancer with mediastinal lymph node metastasis, intranodal growth is regarded as prognostically more favourable than extranodal growth. We evaluated the clinical implications. Mediastinal lymph node metastases removed at mediastinoscopy and/or surgery were classified as intranodal, extranodal or indefinite. "Minimal N2 disease" denoted a solitary, intranodal metastasis, "extranodal" at least one extranodal lymph node metastasis, and "indefinite" more than one intranodal or at least one indefinite metastasis. Although in patients with resected N2 disease, c. 21% of the nodal metastases were "indefinite", survival was significantly better in minimal N2 disease than in the combined groups with extranodal and indefinite lymph node metastases. Of the metastatic nodes removed at mediastinoscopy, 75% were unsuitable for definite classification as only intranodal or extranodal. Only 1 of 49 patients had purely intranodal N2 disease. Thus, it was seldom feasible to classify mediastinoscopic lymph node involvement as intranodal or extranodal, and this classification is unhelpful as regards decisions on thoracotomy. However, when nodal involvement in resected N2 disease was limited to a single node with intranodal growth, the prognosis was better than in patients with extranodal disease or more than one intranodal metastasis or indefinite nodes.