_________________________________________________________________________ Thyroid Dysfunction
Papillary Carcinoma Papillary carcinoma is the most common type of thyroid can- cer, accounting for about 80% of thyroid malignancies [36] . It is also referred to as papillary thyroid cancer or papillary adenocarcinoma. It develops in the thyroid follicle cells and is very slow growing. In 10% to 20% of cases, both lobes of the thyroid gland are involved. There is a good prognosis with this particular cancer, and nearly all individuals with papillary cancer have good long-term survival [36] . Follicular Carcinoma Follicular carcinoma, or follicular adenocarcinoma, is the next most common type of thyroid cancer, although it is much less common than papillary thyroid cancer, making up about 10% of thyroid cancers. This malignancy is less likely to spread to the lymph nodes, but the prognosis is not as good as that seen with papillary carcinoma. Still, follicular carcinoma is not likely to result in death [36] . Other Types Anaplastic carcinoma, also referred to as undifferentiated thyroid cancer, is a rare form of the disease and is believed to develop from existing papillary or follicular cancer. It is extremely aggressive cancer and rapidly invades the neck and metastases to other parts of the body. Anaplastic carcinoma is rare in persons younger than 50 years of age and occurs most often in elderly patients. The associated prognosis is poor [36] . Poorly differentiated thyroid carcinoma has been defined as thyroid cancers that “retain sufficient differentiation to pro- duce scattered follicular structures and some thyroglobulin, but generally lack the usual characteristics of papillary and follicular carcinoma” [37] . The most clearly described type of poorly differentiated thyroid carcinoma is the insular type. Medullary thyroid carcinoma (MTC) is the only cancer that develops from the C cells of the thyroid gland. This cancer can metastasize to the lymph nodes, the lungs, or liver before the thyroid nodule has been found. There are two types of medullary thyroid cancer: sporadic and familial. The sporadic type accounts for 80% of MTC cases. This type of MTC is not associated with a positive family history and occurs most often in a single lobe of the thyroid gland. Familial medullary thyroid carcinoma is seen in patients with a family history of the disease [36] . It is often associated with pheochromocytomas [35] . Thyroid lymphoma is rare but may occur. It does not develop from the C cells or from thyroid follicular cells, but rather from lymphocytes. Thyroid sarcoma is also rare. It begins in the supporting cells of the thyroid and is usually aggressive and difficult to treat [36] .
If goiters are diagnosed, this is an excellent opportunity for patient education regarding iodine consumption. Adults generally require a minimum of 150 mcg of iodine daily, but pregnant and breastfeeding women require an additional 100 mcg daily. Iodized salt contains 1 part iodine to 100,000 parts of salt. The average American ingests 6.2 grams of salt a day; this equates to 474 mcg of iodine if the salt is iodized [33] . THYROID CANCER As discussed, most tumors (95%) that develop in the thyroid gland are benign, but a few are cancerous. Because the thyroid gland is close to the skin, tumors often appear as bumps in the neck. Malignant nodules can develop at any age, but they are most common in adults 30 to 60 years of age, with women often being diagnosed at a younger age than men [7; 35] . While the majority of less aggressive histologic subtypes of thyroid cancer are more common in women than in men, the more aggressive subtypes have similar gender distribution. It is esti- mated that appr oximately 44,020 people (28,615women and 15,405 men) will be diagnosed with thyroid cancer in 2024. The median age at diagnosis is 51 years [34] . • A definitive cause of thyroid cancer has not been identified, but there are certain factors that increase the risk, including [35] : Exposure to high levels of radiation, especially in childhood • Family history of a first-degree relative with thyroid cancer • Inherited conditions, such as familial adenomatous polyposis and multiple endocrine neoplasia type 2 • Female gender • Women who were 30 years of age or older at their last pregnancy • Excess body weight CLASSIFICATION There are several types of thyroid cancer, both differentiated and undifferentiated. Papillary and follicular carcinoma are the most common and are often grouped together to be called differentiated thyroid cancer or well-differentiated thyroid cancer. Oncocytic carcinoma (previously called Hürthle cell carcinoma) is a subtype of follicular carcinoma, accounting for approximately 3% of all thyroid cancers. Other less common types are medullary carcinoma (>5%); anaplastic carcinoma (2%); and thyroid lymphoma, thyroid sarcomas, or other rare tumors (4%) [36].
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Book Code: ANCCTX2027
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