PREDICTORS OF THYROID TUMOR AGGRESSIVENESS

Abstract Thyroid cancers are classified as papillary, follicular (including Hurthle cell), medullary, and anaplastic. Papillary cancers account for about 82% of all thyroid cancers, follicular about 8%, medullary about 6%, Hurthle cell 3%, and anaplastic 1%. The prognosis of patients with papillary thyroid cancer is usually favorable, whereas most patients with anaplastic cancer die within 6 months. The behavior of papillary thyroid cancer can be predicted by patient age, sex, tumor size, local invasion, angioinvasion, lymph node metastases, distant metastases, as well as tumor differentiation and ability to take up radioactive iodine. Thus, older male patients with larger or invasive tumors, with angioinvasion, lymph node or distant metastases, and with tumors that do not take up radioactive iodine or cannot be completely surgically resected have a worse prognosis. Anaploid tumors, tumors with a low adenylate cyclase response to thyroid-stimulating hormone tumors, tumors that are ras-and gsp-positive, and tumors that are p21-positive and p53-positive also appear to behave in a more aggressive manner. In contrast, lymphocytic thyroiditis associated with papillary thyroid cancer predicts fewer recurrences and an improved survival. The treatment of patients with papillary thyroid cancer is controversial primarily because most patients do well with relatively minimal therapy, and there are no prospective studies concerning the merits of various treatments. Much of the controversy relates to the safety of thyroidectomy versus other procedures and, to a lesser extent, when to do a central or modified radical neck dissection. The rate of recurrence is lower, and the death rate may also be lower when patients are treated initially by total thyroidectomy. The rationale for total thyroidectomy is that it enables one to use radioactive iodine to detect and treat local and distant metastases, and it makes serum thyroglobulin determination more sensitive for detecting persistent disease. Total thyroidectomy should be associated with a permanent complication rate of less than 2%. Thyroid-stimulating hormone suppression therapy is recommended by most experts for patients with differentiated thyroid cancer and supported by most clinical and laboratory studies. Central and lateral node selection is recommended for patients with palpable lymphadenopathy.