Thyroid cancers are classified as papillary, follicular (including Hürthle cell), medullary, and anaplastic. Papillary
cancers account for about 82% of all
thyroid cancers, follicular about 8%, medullary about 6%, Hürthle 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.