Thyroid cancer is the most common among the cancers of the endocrine glands. It is more common among women than men. The incidence of thyroid cancer among women is about 6 per 100,000 whereas men have an incidence of about 2.5 per 100,000. In 1995 in the US there were 13,900 new cases of thyroid cancer and 1,120 died from it (Ref.1, p.1629).
Although we speak of thyroid cancer as if it were one type of cancer, it is in reality a collection of very diverse cancers that are classified by their histology, the appearance under the microscope. The reason this is important to know is that the rate, at which the various types of thyroid cancer grow, is vastly different. The faster the cancer grows, the more difficult to control and the deadlier it is. I will explain this in more detail below. There seems to also be a difference whether or not the thyroid cancer is found in a younger or older person. The older the person, the more malignant the growth behavior and the worse the prognosis.
The thyroid gland is situated just below the larynx (voice box) and embraces the trachea (windpipe). The two lobes on each side are connected via the slimmer isthmus, which is the middle part in the front. Many thyroid cancers often start in one of the lobes, but there is a higher risk to develop an identical cancer in the other lobe later in life and this has become important for diagnosis and treatment.
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