Experimental hematogenic metastases of malignant schwannoma in the rat

To study development, growth patterns and morphology of metastatic schwannomas in an animal model, adult Lewis rats were injected intravenously with tissue culture cells derived from a malignant schwannoma induced in a female LEW/mai rat by transplacental administration of ethylnitrosourea (ENU). Groups of animals received a single injection of 0.1 x 10(5); 0.5 x 10(5); 1.0 x 10(5); 5.0 x 10(5); 10 x 10(5) or 100 x 10(5) cells via the femoral vein. The injections resulted in the development of metastatic tumors, primarily involving the lung in all animals. Lung metastases were observed in the form of microscopic and macroscopic peripheral subpleural tumors, central peribronchial and perivascular tumors, parenchymal tumors, diffuse intraalveolar infiltrates and intravascular tumor emboli which were growing. Animals receiving high dosages had a greater variety of forms of the metastatic growth in the lungs than those given low dosages. The animals which received the highest dose had the greatest degree of total lung tumor burden. In 36 of the 60 animals injected, metastatic tumors also developed in the pericardium. Thirteen animals developed metastatic tumors in the kidney, heart, ovary, adrenal, intestine or skeletal muscles. As the cell dosages were increased, more organs became involved, but no tumors developed in the brain.