Malignant Lymphoreticular Tumors Induced by Trypan Blue and Transplanted in Inbred Rats

Abstract

Rats from 5-different strains received subcutaneous injections of 10 mg trypan blue dissolved in water once every 14 days. Tumors of the reticuloendothelial system developed in rats of 3 strains. In an inbred strain of Wistar rats, 19 of 20 had tumors after doses of more than 120 mg dye. Tumors were predominantly in lymph nodes and liver but also in the thymus and kidney and occasionally in the spleen, adrenal, lung, and ovary. During tumor induction, hyperplastic histiocytes in lymph nodes were probably derived from endothelium. The tumors were composed of pleomorphic histiocytes, some binucleate and resembling the Reed-Sternberg cells of human lymphomas. The tumors were transplantable within the same inbred strain, and 1 line was maintained for more than 40 passages. The morphology of the transplantable tumors was identical to that of the primary donor tumor. The distribution of transplanted tumors depended on whether inoculation was subcutaneous or intraperitoneal.