Thyroid cancer is a malignant tumor that originates in the cells of the thyroid gland, a part of the endocrine system. This is a condition of good prognosis if you receive proper therapy early; please see thyroid cancer treatment for additional information. The formation of the malignant tumor occurs when a group of cells in the thyroid gland genetically damaged due to any carcinogenic factor, causing their growth and reproduction behavior to become abnormal.
The Thyroid Gland
The thyroid is a small endocrine gland which regulates many hormonal functions by secretion of triiodothyronine (T3), thyroxine (T4), and calcitonin (thyrocalcitonin). Located at the front of the neck, below the larynx (voice box), it is superficial; any deformation (goiter for instance) can be seen under the skin. It can be the seat of different diseases: hyperthyroidism, hypothyroidism, benign or malignant tumor.
The thyroid gland is divided into two parts, called lobes, located on each side of the trachea. The the lower thirds of the right and left lobes are connected to one another by an end piece of tissue called isthmus. Most cancers develop in the lobes, while less than 3% form in the isthmus. The type of thyroid cancer you are diagnosed with depends on the type of cells affected.
The thyroid gland is composed of two main types of cells:
- Follicular cells (also called epithelial cells or principal cells), which make thyroid hormones that help to control body functions, including heart rate, blood pressure, temperature, and body weight.
Parafollicular cells (also called C cells), which assure neuroendocrine functions. They produce calcitonin, a hormone that helps control calcium and phosphate levels in your blood.
Papillary thyroid cancer (also known as papillary thyroid carcinoma) is the most common cancer of the thyroid gland. It represents approximately 70% of all thyroid cancers. It is well differentiated (as well as follicular carcinoma), it does not cause the cells to lose their ability to bind iodine. Detected early (as is increasingly the case today), the prognosis is quite good, about 97.8% survival rates in the United States; thus, the importance of an early diagnosis and effective thyroid cancer treatment.
The second most common type of thyroid cancer is follicular thyroid carcinoma, which tends to have good survival rates also. Although altered follicular cells can also transform into anaplastic thyroid cancer (a very rapidly and aggressive type of cancer which is resistant to most treatments), it is very uncommon. Follicular thyroid carcinoma is account for about 10%.
Medullary thyroid carcinoma is another type of cancer. The tumor usually forms in the C cells, and represent 5% of all cases of which 25% seem to be hereditary cases.
Other rare types of anaplastic thyroid cancers can also occur: lymphoma, squamous cell carcinoma and Kaposi. They are often serious cases, especially affect older people and represent less than 5% of cases. Early detection is crucial. Please see thyroid cancer symptoms and warning signs for additional info.
Although thyroid cancer is a rare, its incidence is increasing rapidly in many developed countries such as the United States and Canada: about 6.8% per year in men, and 9.5% per year in women since 1998. The good news is that the tumor is often detected at an early stage, and effectively treated. Thanks to advance in screening methods, using medical imaging (ultrasound, magnetic resonance), we can now detect small tumors formerly invisible.