Thyroid Neoplasms
Essentials of Diagnosis
General Considerations
Thyroid cancer accounts for approximately 1.5% of all cancers in the United States. Thyroid cancer, moreover, makes up 92% of endocrine gland cancers and accounts for approximately 12,000 new cases in the United States annually. However, only 1200 people succumb to thyroid cancer each year in the United States, making it one of the more survivable cancers. The incidence of well-differentiated thyroid cancer is approximately 23 times greater in women than in men. Poorly differentiated thyroid cancers are seen in equal proportions in men and women.
The spectrum of malignant thyroid disorders ranges from very indolent tumors, such as most papillary carcinomas, to highly aggressive tumors, such as anaplastic or undifferentiated carcinoma. Papillary carcinoma typically is seen in young adults and often metastasizes regionally to the lymphatics of the neck. Even in the presence of regional metastasis, however, patients with papillary carcinoma have very low mortality rates. Conversely, patients are typically in their sixth or seventh decade when a diagnosis of anaplastic thyroid cancer is made. Only 10% of patients with anaplastic thyroid cancer will survive one year after the diagnosis, with a median survival of approximately 6 months.
Pathogenesis
The two types of cells found in thyroid gland tissue include the neuroendocrine calcitonin-producing C cell (the parafollicular cell) and the follicular cell, derived from the endoderm, which synthesizes thyroglobulin. Thyroid malignancies derive from these two types of cells. Papillary carcinoma, follicular carcinoma, Hƒ