[T(1) carcinoma of the lung: characteristics of lymph node metastasis and its clinical significance].

OBJECTIVE

To investigate the frequency, distribution and features of lymph node metastasis in T(1) carcinoma of the lung, and to provide evidence for lymph node dissection.

METHODS

Two hundred and fifteen patients with T(1) carcinoma of the lung underwent R2 surgery plus extended dissection of hilar, interlobular and mediastinal lymph nodes according to the mapping system developed by Naruke.

RESULTS

1 674 groups of lymph nodes were dissected. The metastatic rates of N(1) and N(2) were 11% and 6% respectively. Lymph node metastatic rates in carcinoma of the lung with maximum diameters less than 1.5 cm and between 1.6 cm approximately 3.0 cm were 5% and 8% respectively. N(1) and N(2) metastasis was not found in squamous cell carcinoma of the lung with a maximum diameter less than 1.5 cm. N(2) metastatic rates were 5% in squamous cell carcinoma 23% in adenocarcinoma and 3/9 in small cell carcinoma, the difference being significant (P < 0.01). 3/4 squamous cell carcinoma invaded only one group of N(2) nodes, but over 3 groups of lymph nodes were positive in 40% of adenocarcinoma. Saltatory metastasis accounted for 41% of N(2) metastasis. Fourteen percent of N(2)-positive tumors in upper lobes metastasized to the lower mediastinum, whereas 60% of N(2)-positive cancers in lower lobes invaded the upper mediastinum.

CONCLUSIONS

The frequency of lymph node metastasis increases with the growth of tumors. Metastasis in adenocarcinoma occurs more frequently than in squamous cell carcinoma, but most common in small cell carcinoma. Tumors at any site can metastasize to the distant mediastinum. Except for squamous cell carcinoma with maximum diameter less than 1.5 cm which are likely to be cured without lymph node dissection, other types of T(1) carcinoma of the lung need extended lymph node dissection.