What is thyroid gland?
Thyroid gland is a butterfly shaped gland located in the front and lower part of the neck. This endocrine gland produces thyroid hormone which is carried by the blood to different parts of the different parts of body. Thyroid hormone helps to maintain body temperature and essential for the normal functioning of brain, heart, muscles and other organs. Deficiency of thyroid hormone is called hypothyroidism while excess production of thyroid hormone leads to hyperthyroidism.
What is thyroid nodule?
The enlargement of the thyroid gland is called as goiter. Thyroid nodule is a swelling developing due to collection of cell lumps or fluid withing thyroid gland. There can be a single or multiple nodules. Thyroid swelling or nodules are very common and can be found in about 50% of elderly population. These nodules are detected by clinical examination or imaging. Thankfully, majority of thyroid nodules are noncancerous, only a small fraction of these nodules may contain thyroid cancer. The exact cause of thyroid nodules is not known. Nodules are commonly associated with Iodine deficiency and inflammation of thyroid gland or thyroiditis.
How is thyroid nodule evaluated?
Once the thyroid nodule is identified, the doctor will advise test based on clinical examination to establish if the nodule is cancerous or benign. Thyroid hormone levels in the blood, ultrasonography of neck and fine needle aspiration cytology (FNAC) are the tests usually recommended. The thyroid cancer occurs mostly in hypo or normal functioning gland and is less likely when gland is over functioning.
Ultrasonography (USG) of neck:
Ultrasound of neck done by an expert sonologist is a useful tool in evaluation of the thyroid nodule. The ultra sound waves help in determining the thyroid tissue architecture. USG is accurate test to know the location of nodule within gland, exact three dimensions, contents of nodule can be solid or fluid filled or cyst like and presence of enlarged lymph glands. There are set guidelines to score the nodule characteristic (TIRADS score), which help sonologist to suggest if the nodule is cancerous or not. Any suspicious nodule is considered for a fine needle aspiration cytology test.
Fine needle aspiration cytology (FNAC):
This is a simple office procedure, where a fine injection needle is used to aspirate a few cells from the nodule. Local anaesthesia may be used; however, the needle is so fine that this may not be required. The procedure is usually done under guidance of an ultra sound to get cells from most suspicious location. Patient goes home with a small band aid immediately following procedure.
The cells collected are examined under microscope by a trained pathologist. The findings are graded according to Bethesda scoring system for thyroid. The lower score is associated with a noncancerous nodule while a score of 6 confirms cancer.
Thyroid scan is done to determine the function of gland. It is usually not required for the diagnosis of cancer. In patients with increased hormone production, thyroid scan helps to identify the over functioning part of the thyroid gland.
A number of gene tests are available to confirm the diagnosis of thyroid cancer. These additional tests are required if the FNAC report is inconclusive but there is high suspicion of cancer, but seldom required in practice.
What are symptoms of thyroid cancer?
Thyroid cancer usually detected as painless swelling in neck. The patients often notice it as a neck swelling in front of a mirror or someone else finds a moving bulge while swallowing. Larger nodule may cause heaviness or pain in neck. Cancer can compression oesophagus (food pipe) or trachea(windpipe) and may lead to swallowing and breathing difficulty. Rarely voice may become hoarse due to the nerve to voice box getting affected. More commonly the nodules are incidentally detected during scans done for some other ailments.
What are types of thyroid cancer?
- Differentiated thyroid cancers are the most common types accounting for 90-95% of all thyroid cancers. Papillary and follicular thyroid cancer are the two sub types of differentiated thyroid cancers. Papillary being most common accounting for 70-80%, remaining 15-20% being follicular variant. Papillary carcinoma is more likely to spread to the neck lymph node, while with follicular carcinoma is likely to spread to distant sites to involve lung and bone.
- Medullary cancer is a rare type of thyroid cancer. About 25% of medullary carcinoma is genetic associated with RET mutation. Patient’s close family members are advised to undergo blood to detect RET mutation. Hormone calcitonin is secreted by medullary carcinoma and is a useful marker of the disease.
- Anaplastic thyroid cancer is a very aggressive variant. Thankfully is a rare occurrence. This variant usually does not respond well to treatment.
Treatment of thyroid cancer:
Treatment of thyroid cancer require a multi-disciplinary management with a core team comprising of a head and neck surgeon, endocrinologist, nuclear medicine physician supported by a trained sonologist and pathologist.
- Surgery:The primary treatment thyroid cancer is surgery. The extent of surgery is determined by the best neck oncologist in Bangalore based on various factors as per the guidelines. Surgery may involve removal of one lobe (lobectomy), both lobes (total thyroidectomy), surrounding lymph glands (central compartment or lateral neck dissection). The most important part of the surgery is to preserve nerve to voice box and parathyroid glands required to maintain calcium levels.
- Radioactive Iodine (I131) therapy: Thyroid cells and differentiated thyroid cancer cells concentrate iodine. Radioactive Iodide can be used to kill small remaining thyroid tissue or tumor tissue using Iodine therapy. This therapy is specific for thyroid and side effects due to damage to other organs is minimal.
- Radiation and targeted therapy: These are usually restricted to advanced, aggressive and resistant disease.
- Thyroid supplementation: Following complete removal of the thyroid gland, replacement of thyroid hormone is necessary. Thyroid supplements at a set dose are given empty stomach every day.
- Thyroglobulin monitoring
Outcomes of thyroid cancer:
Majority of thyroid cancers have good outcomes. It is important to keep a regular follow up with regular clinical examination, blood test and scans as advised by the doctor at the best head & neck oncology hospital in Bangalore