 Additional data suggest that many, if not most, anaplastic thyroid cancers express PDGF receptors, and that these receptors are functional. Since activation of PDGF receptors is associated with the growth of other tumors and c-Abl is overexpressed in p53-mutated anaplastic thyroid carcinoma cell lines, it seems appropriate to test Gleevec as a therapy for patients with anaplastic thyroid cancer. The specific hypothesis to be tested is that anaplastic thyroid cancers that overexpress PDGF receptors or Abl will respond to Gleevec therapy. The lack of any accepted efficacious therapies for anaplastic thyroid cancer, the poor prognosis of this cancer, and the relatively low toxicity of Gleevec justify this proposed trial. 