Thyroid cancer

Thyroid cancer is a heterogenous group of diseases that accounts for most of endocrine cancer-related deaths. It is the most common endocrine malignancy; however its relative incidence and death rate compared with other cancers is low, representing only 1% of all cancers and only 0.05% of all cancer-related deaths. The American Cancer Society estimates that 18 400 new cases of thyroid cancer will occur in the United States in 2000; 13 700 in women and 4700 in men. An estimated 1200 deaths related to thyroid cancer occurred in 2000; 700 in women and 500 in men. The median age at diagnosis is 45 to 50 years but it does occur in the very young as well as in the elderly. The cause of thyroid cancer is not known but childhood exposure to radiation and iodine deficiency have been identified as risk factors.

The various types of thyroid cancers have different pathologic features, disease courses, and patterns of recurrence. Thyroid cancers are commonly categorized as well-differentiated thyroid cancer (papillary and follicular), medullary thyroid cancer, and anaplastic thyroid cancer. Less common are thyroid lymphoma and metastatic disease to the thyroid.

Well-differentiated thyroid cancers

Papillary and follicular thyroid cancers are well-differentiated malignant neoplasms that arise from follicular cells. In general, they are considered indolent malignancies with favorable long-term survival rates; however, certain patient subsets such as elderly patients with advanced disease may experience rapid tumor progression.