FTC-133 was isolated from a lymph node metastasis of a follicular thyroid carcinoma. The morphology differs from flat polygonal to spindle formed cells. They retained differentiated thyrocyte function and thyrocyte responsiveness to thyrotropin and local active growth factors. Thyroglobulin immunoreactivity could be shown in the cytoplasm and EGF receptor immunoreactivity could be visualised on the cell membranes. Complex chromosomal changes were detected as well as a p53 mutation.