General and more comprehensive text about cancer diseases, their behavior, causes and treatment can be found here.
Malignant tumors of the thyroid gland belong among less common cancers. In addition, they are relatively well treatable and they do not have a high mortality. However, early detection is essential.
First it is important to know some information about the thyroid gland. It is a glandular tissue located deep in the neck with a close anatomical relationship to larynx and upper trachea. Histologically, the gland includes two main types of cells – follicular and parafollicular cells.
The follicular cells produce the thyroid hormones and they represent the majority of thyroid cells. Three types of cancers develop from follicular cells – follicular, papillary and anaplastic cancer. Follicular and parafollicular cancers are more common and they have better prognosis. Their cells are usually well differentiated and they maintain the ability to actively capture iodine molecules from the blood such as the healthy thyroid cells. The anaplastic cancer is very dangerous, its cells are immature (unable to scavenge iodine), rapidly proliferate and rapidly metastasize.
The parafollicular cells produce a hormone known as calcitonin. Calcitonin is important for proper metabolism of calcium in our body. Parafollicular cells give rise to a so-called medullary thyroid cancer. Since it does not come from the follicular cells, it is unable to scavenge the iodine from the blood.
Malignant tumors of follicular cells
- Papillary type - can recapture iodine, relatively little dangerous
- Follicular type - can recapture iodine, relatively little dangerous
- Anaplastic type - can not recapture iodine, very dangerous
Malignant tumors of parafollicular cells
- Medullary type - can not recapture iodine, low-moderate dangerous
The cause if the thyroid cancer is usually unknown. It is assumed that its development may be related to exposure to radiation and its incidence in Europe reportedly grew after the nuclear catastrophe at the Chernobyl nuclear power plant. Genetic factors also can not be excluded as the tumors may have familial occurrence. The thyroid cancer is slightly more common in women.
The tumor may manifest as a palpable nodule in the neck. Larger tumors may compress surrounding tissues leading to swallowing disorders (esophagus), hoarseness and shortness of breath (vocal cords, respiratory tract). Malignant tumors may infrequently change the thyroid gland function, but this is much rarer situation that in local benign tumors. Both symptoms of overactive and underactive thyroid gland may occur in such case. Increased activity of thyroid gland is more typical for cancers, whose cells have retained ability to scavenge iodine and produce thyroid hormones. On the contrary, decreased thyroid function occurs in more dangerous aggressively growing tumors that directly destroy the thyroid gland tissue. Local metastases may cause painless enlargement of neck lymph nodes.
The tumor may be palpated in the neck as a mass of an unknown origin. The blood tests may (or may not) show changes of concentrations of thyroid hormones. The tumor may be visualized by neck ultrasound and its local extent with affection of cervical lymph nodes can be examined by computed tomography. The approach depends on the histological type and behavior of the tumor and therefore, biopsy of the tumor tissue should be performed.
The only mean of prevention is avoidance of sources of radioactivity. When you touch a lump in the neck, you should visit your doctor as soon as possible.
The primary treatment is surgical, i.e. removal of the tumor mass. Usually, the operation removes the whole thyroid tissue (thyroidectomy). Tumors, whose cells have the ability to scavenge and accumulate iodine, may be also treated by radioactive iodine 131. This substance is administered to the patient, it circulates in the body and it is actively taken and accumulated by the tumor cells including metastases. The cells are damaged by the radioiodine and succumb to necrosis. This therapy is ineffective in thyroid cancers without the ability to recapture the iodine.