Sunday, November 1, 2009

THYROID CANCER

Thyroid neoplasm or thyroid cancer usually refers to any of four kinds of malignant tumors of the thyroid gland: papillary, follicular, medullary or anaplastic. Most patients are 25 to 65 years of age when first diagnosed; women are more affected than men. Papillary and follicular tumors are the most common. They grow slowly and may recur, but are generally not fatal in patients under 45 years of age. Medullary tumors have a good prognosis if restricted to the thyroid gland and a poorer prognosis if metastasis occurs. Anaplastic tumors are fast-growing and respond poorly to therapy.

Thyroid nodules are diagnosed by ultrasound guided fine needle aspiration (USG/FNA) or frequently by thyroidectomy (surgical removal and subsequent histological examination). As thyroid cancer can take up iodine, radioactive iodine is commonly used to treat thyroid carcinomas, followed by TSH suppression by high-dose thyroxine therapy.

After a nodule is found during a physical examination, a referral to an endocrinologist, a thyroidologist or otolaryngologist may occur. Most commonly an ultrasound is performed to confirm the presence of a nodule, and assess the status of the whole gland. Measurement of thyroid stimulating hormone and anti-thyroid antibodies will help decide if there is a functional thyroid disease such as Hashimoto's thyroiditis present, a known cause of a benign nodular goiter.

Fine needle biopsy

One approach used to determine whether the nodule is malignant is the fine needle biopsy (FNB), which some have described as the most cost-effective, sensitive and accurate test.

FNB or ultrasound-guided FNA usually yields sufficient thyroid cells to assess the risk of malignancy, although in some cases, the suspected nodule may need to be removed surgically for pathological examination.

Rarely, a biopsy is done using a large cutting needle, so that a piece of nodule capsule can be obtained.

Blood tests

Blood or imaging tests may be done prior to or in lieu of a biopsy. The possibility of a nodule which secretes thyroid hormone (which is less likely to be cancer) or hypothyroidism is investigated by measuring thyroid stimulating hormone (TSH), and the thyroid hormones thyroxine (T4) and triiodothyronine (T3).

Tests for serum thyroid autoantibodies are sometimes done as these may indicate autoimmune thyroid disease (which can mimic nodular disease).

Imaging

The blood assays may be accompanied by ultrasound imaging of the nodule to determine the position, size and texture, and to assess whether the nodule may be cystic (fluid filled). Also suspicious findings in a nodule are hypoechoic, irregular borders, microcalcifications, or very high levels of blood flow within the nodule. Less suspicious findings in benign nodules include, hyperechoic, comet tail artifacts from colloid[clarification needed], no blood flow in the nodule and a halo, or smooth border.

Some clinicians will also request technetium (Tc) or radioactive iodine imaging of the thyroid. An 123I scan showing a hot nodule, accompanied by a lower than normal TSH, is strong evidence that the nodule is not cancerous.

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