Carcinoma types of the thyroid gland
There are four forms of malignant thyroid tumors:
- Papillary thyroid carcinoma
This form, which occurs in 5% of all thyroid carcinomas, is also known as C-cell carcinoma. The tumor originates from the calcitonin-producing cells of the thyroid gland and not, like all other types of carcinoma listed, from the thyroid hormone-producing cells. It therefore does not store iodine.
Calcitonin causes, among other things, the incorporation of phosphate and calcium into the bones. Metastases are scattered in the lymphatic and bloodstream from the primary tumor. The prognosis of C-cell carcinoma is relatively good.
In the majority of cases, this carcinoma occurs sporadically and has an age peak at 50-60 years. In 20% of cases, however, inheritance can be found in the family of the patient. Some of these familial tumors occur within the MEN; in this disease, other carcinomas are found in endocrine, i.e. hormone-producing organs, such as the pancreas or the adrenal gland. A distinction is made between three forms of MEN, which, depending on the type, occur between the ages of 10 and 50.
- Medullary thyroid carcinoma
Prognosis
The prognosis of thyroid cancer is highly dependent on the stage of the cancer and the type of cancer cells that are predominant. Early detected papillary or follicular thyroid cancer generally has a good prognosis. After surgical removal of half or all of the thyroid gland, a subsequent radioiodine therapy that kills all remaining cancer cells and the daily intake of hormone replacement tablets, one can speak of a cure.
In some cases, despite successful therapy, a new cancer formation (recurrence) occurs. In order to be able to detect and treat a recurrence of cancer at an early stage, regular aftercare should be carried out. In contrast, the prognosis of medullary or anaplastic thyroid cancer is significantly worse.
These are types of cancer that bear little resemblance to the original thyroid tissue and are therefore often discovered later and respond less well to therapies (e.g. radioiodine therapy). They also metastasize earlier. In medullary thyroid cancer, the probability of survival for the next 10 years is about 50-70%, whereas patients with anaplastic cancer often only have a few months to a year to survive.
However, it should not be overlooked that all prognosis statements are only average values and individual survival can vary considerably. The chances of cure for thyroid cancer vary greatly depending on the cell type of the dominant cancer cell, the spread and the stage the cancer is already in at the time of diagnosis.On the one hand there are the well differentiated papillary and follicular cancers of the thyroid cancer, which behave exactly like the healthy thyroid cells, store iodine and can therefore usually be diagnosed quite early. On the other hand, there are medullary and undifferentiated anaplastic cancers.
Here, iodine storage does not occur, which is why the diagnosis is often made much later and a therapy can therefore often not be initiated in time. In most cases, a late diagnosis leads to significantly lower chances of recovery, since extensive metastasis (metastasis/diffusion of cancer cells throughout the body) may already be present. See: Metastases in thyroid cancer The papillary and follicular thyroid cancer has, however, in principle quite good chances of recovery if it is detected early.
About 90% of patients can be cured by surgical removal of the thyroid (thyroidectomy) and subsequent radioiodine therapy to remove remaining or scattered cancer cells. Additional chemotherapy is usually not necessary. Since the thyroid gland produces vital hormones, these must be taken daily as tablets after a thyroidectomy to compensate for the loss.
If this is done regularly about an hour before breakfast, it is possible to live very well without a thyroid gland. In rare cases, cancer recurs after some time despite the removal of the thyroid gland (recurrence) because small cancer cells have not been completely removed. This usually happens with differentiated, frequently occurring types of cancer.
In order to keep the risk of this recurrence as low as possible, annual follow-up examinations in the form of a neck ultrasound and a tumor marker determination from the blood are performed after thyroidectomy due to thyroid cancer. By and large, however, the chances of recovery from thyroid cancer depend on the time of diagnosis: The earlier the cancer is detected, the higher the chance of recovery. This applies to each of the four types of thyroid cancer cells.
Life expectancy for thyroid cancer also depends on the type of cancer, the degree of metastasis (the extent to which cancer cells are spread throughout the body) and the stage the cancer is at when diagnosed. Life expectancy is most often described by the 10-year survival rate (10-YR). However, these are only average values that have been calculated from experience reports.
Individually, life expectancy can differ significantly from the 10-YEAR survival rate. The most common thyroid cancer is also the one with the best life expectancy: papillary thyroid carcinoma (carcinoma means cancer). Since its growth is restricted exclusively to the thyroid tissue, it can be completely removed by surgical removal of the thyroid gland in most cases, thus curing the patient.
Here, the 10-year survival rate is about 90%. Patients with follicular thyroid cancer have a slightly reduced 10-Year survival rate of 80% due to the possible hematogenic scattering (scattering of cancer cells in the bloodstream). The 10-YEAR of patients with medullary thyroid cancer is about 50-70%.
In this context, it is of particular importance in which stage the cancer was discovered and whether there is a pronounced metastasis (scattering of cancer cells). Patients with an anaplastic or undifferentiated tumor have a significantly lower life expectancy. Due to its very rapid growth, which is not restricted to the thyroid gland, and early cancer cell settlement in the bone, liver, brain and lung, the average life expectancy in this case is only about one year.
In addition to the stage at diagnosis and the type of cancer, the degree of metastasis (degree to which the cancer cells spread in the body) also has an influence on life expectancy in thyroid cancer. The cancer may have spread either through the lymphatic or bloodstream. Affected regional neck lymph nodes can usually be removed easily during surgical thyroidectomy and thus no longer have a shortening effect on life expectancy.
However, metastases that already occur in organs such as the lungs, liver, brain and bones cannot be treated easily and can therefore lead to a shortened life expectancy. In this case, only targeted radiation or systemic chemotherapy can have a positive effect on the patient.The term “metastasis” means the metastasis or scattering of cancer cells to parts of the body other than their place of origin, as well as the development of daughter tumors. This can occur via the lymphatic or bloodstream.
At first, the cancer grows restricted to the thyroid gland. At this point, there is no metastasis. However, when the cancer reaches a size that exceeds the size of the organ capsule surrounding the thyroid gland, it breaks through and attacks neighboring organs (trachea and esophagus), neighboring structures (larynx and vocal fold nerves) and regional lymph nodes.
If the growth continues, the cancer cells also spread in the blood (hematogenic metastasis) and can thus reach, settle and multiply in distant organs or body areas. In this case one speaks of distant metastasis. In thyroid cancer, frequent metastasis sites are the liver, lungs, brain and bones.
However, the four different types of cancer also show differences in metastasis:
- In the late stage, papillary thyroid cancer usually spreads only through the lymphatic system, which is why it has a good prognosis after surgical removal of the thyroid gland with removal of the cervical lymph nodes. Only in children, papillary thyroid cancer can cause metastases in the lungs in its early stages, which can be treated well if detected in time.
- Advanced follicular thyroid cancer, on the other hand, often spreads through the bloodstream. In this case, distant metastasis often occurs, mostly in the lungs or bones.
- A medullary thyroid cancer usually forms metastases in the cervical lymph nodes and in the upper thoracic region at a very early stage. In later stages, it also leads to a settlement of daughter tumors in the lungs, liver and bones.
- Anaplastic cancer spreads to the lungs, liver, bones and brain at an early stage and therefore has the worst prognosis.
