Thoracic lymph node metastasis and carcinomatous lymphangitis after inoculation of Walker 256 tumor through the trachea.

1. Experimental models of carcinomatous lymphangitis have not been described. This is an important clinical entity which usually results in the patients' death, although its natural history is still controversial. This study was undertaken to investigate whether the pattern of lung involvement after Walker 256 tumor inoculation through the trachea is a good model of carcinomatous lymphangitis. 2. Fifty male Wistar rats were inoculated through the trachea with 2.5 x 10(6) Walker 256 tumor cells and killed in groups of 5 animals each at 6 h and on days 1, 3, 7, 14, 21, 28, 35, 45, and 60 of the experiment. The lungs and thoracic lymph nodes were examined by light microscopy. 3. There were no tumors in the 25 animals killed before the 21st day of the experiment. The remaining 25 rats were sacrificed after 3 weeks of the experiment; 52% of them displayed thoracic lymph node metastases, and 40% developed a mild carcinomatous lymphangitis. The lung involvement did not correlate with respiratory distress, tumor dissemination or additional histological abnormalities. 4. We conclude that invasion of the lung is possible after intratracheal tumor cell inoculation, and that spreading follows a lymphatic pattern. This finding establishes this approach as a viable experimental model of carcinomatous lymphangitis. New approaches to increase the intensity and frequency of lung involvement, as well as the development of respiratory distress should be pursued in order to improve the efficiency of this model.