Although they comprise fewer than 1% of all gastrointestinal (GI) tumors, gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the GI tract. It has been estimated that there are 3,300 to 6,000 new GIST cases per year in the United States. A study based on Surveillance, Epidemiology and End Results (SEER) registry data found that the age-adjusted yearly incidence of GIST in the United States was 6.8 per million from 1992 to 2000. However, the...
Carcinoma of the thyroid gland is an uncommon cancer but is the most common malignancy of the endocrine system. Differentiated tumors (papillary or follicular) are highly treatable and usually curable. Poorly differentiated tumors (medullary or anaplastic) are much less common, are aggressive, metastasize early, and have a much poorer prognosis. Thyroid cancer affects women more often than men and usually occurs in people between the ages of 25 and 65 years. The incidence of this malignancy has been increasing over the last decade. Thyroid cancer commonly presents as a cold nodule. The overall incidence of cancer in a cold nodule is 12% to 15%, but it is higher in people younger than 40 years and in people with calcifications present on preoperative ultrasonography.[3,4]
Patients with a history of radiation administered in infancy and childhood for benign conditions of the head and neck, such as enlarged thymus, acne, or tonsillar or adenoidal enlargement, have an increased risk of cancer as well as other abnormalities of the thyroid gland. In this group of patients, malignancies of the thyroid gland first appear beginning as early as 5 years following radiation and may appear 20 or more years later. Radiation exposure as a consequence of nuclear fallout has also been associated with a high risk of thyroid cancer, especially in children.[6,7,8] Other risk factors for the development of thyroid cancer include the following:
A history of goiter.
Family history of thyroid disease.
The prognosis for differentiated carcinoma is better for patients younger than 40 years without extracapsular extension or vascular invasion.[10,11,12,13,14] Age appears to be the single most important prognostic factor. The prognostic significance of lymph node status is controversial. One retrospective surgical series of 931 previously untreated patients with differentiated thyroid cancer found that female gender, multifocality, and regional node involvement are favorable prognostic factors. Adverse factors included age older than 45 years, follicular histology, primary tumor larger than 4 cm (T2–T3), extrathyroid extension (T4), and distant metastases.[15,16] Other studies, however, have shown that regional lymph node involvement had no effect [17,18] or even an adverse effect on survival.[13,14,19] Use of sentinel lymph node biopsy may aid in identifying patients with occult metastases who might benefit from central neck dissection.
Diffuse, intense immunostaining for vascular endothelial growth factor in patients with papillary cancer has been associated with a high rate of local recurrence and distant metastases. An elevated serum thyroglobulin level correlates strongly with recurrent tumor when found in patients with differentiated thyroid cancer during postoperative evaluations.[22,23] Serum thyroglobulin levels are most sensitive when patients are hypothyroid and have elevated serum thyroid-stimulating hormone levels. Expression of the tumor suppressor gene p53 has also been associated with an adverse prognosis for patients with thyroid cancer.