Cancer
Whether a cancerous disease is present cannot be determined by scintigraphy of the thyroid gland. It can only give clues. If, for example, a thyroid node that is palpable or discovered by ultrasound shows only weak activity in the scintigraphy (cold node), it may be a cancer.
In order to gain information, a so-called fine needle biopsy is usually recommended. By examining the cells obtained, the suspicion can be substantiated or not. Radiation exposure from the scintigraphy of the thyroid gland itself is too low to pose a serious risk of cancer development.
Cold knot
A cold node in the thyroid is present when a region of the thyroid gland absorbs no radioactivity at all or at least significantly less radioactivity than the rest of the thyroid gland during scintigraphy. In the scintigraphy image (scintigram), this is usually shown as an area that stands out in color from the rest of the thyroid. Accordingly, it is tissue that does not produce thyroid hormones.
For example, it could be a harmless water-filled cyst. However, since thyroid cancer may be present in some cases, cold nodules should be examined by sampling for safety. This is done by a so-called fine needle biopsy.
Under local anesthesia and under visual control by an ultrasound probe, the doctor uses a long needle to take a tissue sample from the node. If abnormal cells are found, surgical removal of the thyroid gland is usually recommended. The name of the cold node is not due to a difference in temperature, but to the representation in the scintigraphy. Weak radioactivity is usually shown in blue.
Hot knot
If an area of stronger radioactivity is visible in the scintigraphy, it is called a hot node. The higher the radioactive radiation, the redder the node is shown. This is the reason for the name and not an actual difference in temperature.
There is also no connection to a possible inflammation. Hot nodules stand for thyroid gland areas with increased activity, i.e. increased thyroid hormone production. They are so-called autonomous nodes or focal autonomies.
These are areas that produce excessive hormones independently of the body’s control mechanisms. If these are particularly active, signs of hyperfunction such as trembling, palpitations, restlessness and many more can appear. They can be cured by surgery or radiotherapy with radioactive iodine (radioiodine therapy). Malignant disease is unlikely to occur with hot nodules, as long as there are no additional cold nodules. Therefore, in the case of hot nodules, fine needle biopsy (taking samples to examine for altered cells) is generally not advisable.
