An anaplastic thyroid cancer cell line, Thena, was recently established in our laboratory following radical thyroidectomy of a patient with anaplastic thyroid cancer. Microscopically, Thena cells were spindle-shaped or small round cells. Thena cells were reactive with cytokeratin AE1/ AE3 antibodies, epithelial membrane antigen, interleukin (IL)-6, epithelial growth factor receptor, transforming growth factor (TGF)-, vascular endothelial growth factor, and vimentin. Thena cells secreted high levels of IL-6, leukemia inhibitor factor (LIF), tumor necrosis factor (TNF)-, and TGF-1 in the culture supernatants, as determined by enzyme-linked immunosorbent assay. When subcutaneously injected with Thena cells, athymic nude mice developed tumor masses in the skin within 2 weeks. Furthermore, Thena cells induced cachexia in these tumor-bearing mice. High levels of human IL-6, LIF and TGF-1 were detected in the mouse sera. To our knowledge, the Thena cell line is the first thyroid cancer cell line reported to induce cachexia in nude mice. This cachectic animal model is worthy of further study to explore the treatment of thyroid cancer-induced cachexia.