ObjectiveTo establish an animal model of anaplastic thyroid cancer with high metastatic activity as in human body. MethodsHuman anaplastic thyroid cancer cell line TAK was injected into one of the lateral lobes of the thyroid gland, as well as in the subcuitis in a series of nude mice. Mice were sacrificed when found moribund, and autopsy and histology were performed subsequently.ResultsThe implantation of human anaplastic thyroid cancer cells in an ectopic enviroment did not permit expression of metastasis potential. In contrast, intrathyroid implantation did. Lymph node (5/10), lung (3/10) and one metastasis (1/10) were noted upon histological examination. ConclusionAn animal model with high metastatic activity is established when human anaplastic thyroid cancer cell line TAK is implanted orthotopically into nude mice.