Management of undifferentiated thyroid cancer

Management of thyroid carcinoma relies upon the tumour cells maintaining th e differentiated functions that are typical of normal thyroid follicular ce lls, such as: dependence upon thyrotropin for growth, production of thyrogl obulin and effective transport of iodine. Likewise, differentiated thyroid carcinomas often exhibit an auspicious clinical behaviour with a slow rate of growth and low potential for invasion and distant metastasis. These feat ures permit therapy of disseminated tumour, effective follow-up surveillanc e and the assumption of a good prognosis. As each of these features are los t, the opportunities for both disease status assessment and therapeutic int ervention diminish accordingly. A major obstacle is our failure to define e ffective systemic treatments to replace radioiodine therapy, whose loss is consonant with the loss of iodine transport and retention. The extreme of u ndifferentiated clinical behaviour is epitomized by anaplastic thyroid carc inoma, a rare, terminally dedifferentiated malignancy that is rapidly and i nvariably fatal. It is important to be attuned to clinical clues suggesting the presence of dedifferentiated tumour and related prognostic signs. This allows the application of currently limited therapeutic options and define s the need for research to develop new systemic treatments.