Thyroid
Thyroid Cancer
There are four main types of thyroid cancer.
1. PAPILLARY THYROID CANCER: This is the most common type of thyroid cancer and is typically seen between the ages of 20 and 50. It occurs approximately three times more frequently in women than in men. It is also the most common type of thyroid cancer found in children under the age of 14. Approximately 90% of all thyroid cancers are papillary thyroid cancers.
These tumors often remain smaller than 1 cm for many years (sometimes up to 30 years) without growing or causing any symptoms. They are frequently discovered incidentally when the thyroid gland is surgically removed for another reason, such as goiter or hyperthyroidism. In recent years, they have also been detected more frequently during routine health check-ups thanks to the widespread use of high-resolution ultrasound examinations.
In one of our studies conducted in Turkey, papillary thyroid cancer was found in approximately 2% of the general population, with most individuals being unaware that they had the disease. In some countries, such as Japan and Finland, this rate has been reported to be as high as 30% of the population. This has been associated with high consumption of seafood, leading to excessive iodine intake, which may contribute to inflammation of the thyroid gland and the subsequent development of cancer in the inflamed tissue.
In a thyroid gland that has been completely removed due to papillary thyroid cancer, an unencapsulated, dirty-white tumor focus is observed in the left thyroid lobe.
Papillary thyroid cancer is treated surgically, and the standard treatment is total thyroidectomy (complete removal of the thyroid gland). In patients whose tumor is a microcarcinoma measuring less than 10 mm, postoperative treatment generally consists only of thyroid hormone replacement therapy, and no additional treatment is required.
However, radioactive iodine (RAI) therapy should be administered approximately six weeks after surgery if any of the following conditions are present:
- The cancer has spread to the lymph nodes.
- The tumor has invaded the thyroid capsule.
- The tumor measures more than 10 mm in diameter.
Radioactive iodine therapy reduces the risk of both local recurrence in the neck and distant metastasis.
If lymph node involvement is present in the neck, the affected lymph nodes should be removed en bloc together with the thyroid gland. If lymph node involvement is suspected before surgery, the lymph node should not be surgically removed beforehand. If confirmation is necessary, the diagnosis should be established by fine-needle aspiration biopsy (FNAB), preserving the tissue integrity so that the thyroid gland and the involved lymph nodes can be removed together during the definitive operation. This procedure is known as total thyroidectomy with modified radical neck dissection or functional neck dissection.
Patients are monitored after treatment using TSH (thyroid-stimulating hormone) and thyroglobulin levels. While the TSH level reflects the adequacy of thyroid hormone replacement therapy, a thyroglobulin level close to zero generally indicates successful treatment with no remaining thyroid tissue or recurrent disease. However, in some cases, recurrence may occur even without an increase in thyroglobulin levels.
Approximately 90% of patients resume normal, healthy lives following successful treatment, making papillary thyroid cancer one of the cancers with the most favorable prognosis.
2. FOLLICULAR THYROID CANCER
Follicular thyroid cancer occurs most commonly in women between the ages of 40 and 60 and accounts for approximately 5% of all thyroid cancers.
Among thyroid cancers, follicular carcinoma is one of the most difficult to diagnose. Neither fine-needle aspiration biopsy (FNAB) performed before surgery nor intraoperative frozen section examination can reliably determine whether the lesion is malignant.
The reason is that the diagnosis depends on demonstrating that tumor cells have penetrated through the capsule surrounding the tumor. Since the tumor cells themselves often appear similar to normal thyroid cells under the microscope, malignancy cannot be confirmed unless capsular invasion (or vascular invasion) is identified during the detailed examination of the entire surgical specimen.
- If the tumor invades the capsule, it is diagnosed as follicular thyroid carcinoma.
- If the capsule remains completely intact, the lesion is diagnosed as a benign follicular adenoma.
In a thyroid gland that has been completely removed because of a follicular tumor, an encapsulated tumor focus is observed in the left thyroid lobe.
The treatment for follicular thyroid cancer is similar to that of papillary thyroid cancer and consists of total thyroidectomy. If the cancer is confirmed to be invasive, postoperative radioactive iodine (RAI) therapy is recommended regardless of the size of the tumor. Approximately 80% of patients go on to live normal, healthy lives following successful treatment.
3. MEDULLARY THYROID CANCER
The familial (hereditary) form of medullary thyroid cancer typically occurs between the ages of 1 and 20, whereas the sporadic (non-hereditary) form usually develops after the age of 40 and is often diagnosed after it has already spread to the lymph nodes. Medullary thyroid carcinoma accounts for approximately 5% of all thyroid cancers.
The standard treatment is total thyroidectomy combined with lymph node dissection on the side of the neck where the tumor is located.
Unlike papillary and follicular thyroid cancers, radioactive iodine therapy is not used after surgery because medullary thyroid cancer arises from parafollicular (C) cells, which do not absorb iodine.
During follow-up, the blood calcitonin level is an important tumor marker used to monitor for persistent or recurrent disease.
Approximately 60% of patients are able to maintain a normal, healthy life after successful treatment.
Total thyroidectomy specimen removed for medullary thyroid cancer in the left thyroid lobe, together with the neck lymph node dissection specimen from the same side.
4. ANAPLASTIC THYROID CANCER
Anaplastic thyroid cancer is the most aggressive form of thyroid cancer. It accounts for approximately 1% of all thyroid cancers.
It typically develops in patients over the age of 60 and is thought to arise when long-standing, untreated papillary or follicular thyroid cancers undergo a sudden biological transformation, becoming highly aggressive and rapidly enlarging.
By the time of diagnosis, the disease is usually too advanced for curative surgery. In such cases, radiotherapy to the neck may be administered as a palliative treatment to relieve symptoms and improve the patient's quality of life.
Anaplastic thyroid cancer demonstrating rapid growth with extension to the skin surface. In most cases, this type of cancer is too advanced to be treated surgically.
Postoperative specimen following total thyroidectomy with central and lateral neck dissection for metastatic thyroid cancer.
Appearance of the right side of the neck after removal of the thyroid gland and cervical lymph nodes. From left to right in the image: the vein, the nerve, the artery (held with forceps), and the trachea.
Closure of the surgical incision and placement of a surgical drain after the operation.
Neck dissection
Bilateral total thyroidectomy and bilateral neck lymph node dissection.
