Thyroid Cancer

Thyroid cancer is cancer affecting the thyroid, a butterfly-shaped gland at the base of the neck that produces hormones that control your heart rate, blood pressure, body temperature and weight. It is the 8^th most common cancer affecting women in Singapore.

Types of Thyroid Cancers

Thyroid cancers are classed according to their cell types

• Papillary thyroid cancer – This is the most common form that comes from the thyroid follicles.
• Follicular thyroid cancer – Also from thyroid follicles, it may be difficult to tell apart from non-cancerous thyroid nodules.
• Medullary thyroid cancer – This is a rare form of cancer that come from the cells located between thyroid follicles.
• Anaplastic thyroid cancer – While rare, this form of cancer is aggressive and has a poorer recovery rate.
• Thyroid lymphoma – A rare form of cancer, also known as non-Hodgkin lymphoma, that affects the white blood cells (lymphocytes).

Causes

Thyroid cancer may affect both the young and old. They are usually readily treatable and have very good cure rates, especially in younger patients.

Mutations of certain genes have been known to cause papillary and follicular thyroid cancer. Unfortunately, it is not clear what causes these gene mutations, although over-exposure to radiation is a well-established cause. Certain inherited medical conditions like hereditary polyposis and type 2 multiple endocrine neoplasia (rare) are linked to thyroid cancers as well.

You should see an endocrinologist (hormone specialist) for assessment. Every thyroid lump or nodule should be evaluated by ultrasound, which is affordable, safe and easily available. Ultrasound scans allow doctors to accurately measure the size of a nodule. Certain sonographic features may help to tell the differences between benign (non-cancerous) and cancerous nodules. Nodules that are small (below 1cm), well-defined or contain mostly fluid are likely benign. Hypoechoic nodules that appear tall with uneven borders, microcalcifications (small calcium build-up), hypervascularity (increased number of blood vessels) and more than 4cm with swollen lymph nodes are more likely to be cancerous. Thyroid function and thyroid antibodies should also be tested through blood tests as higher levels of thyroid stimulating hormone and antibodies are linked with a greater chance of cancer.

Determining if a Thyroid Nodule is Cancerous

All nodules more than 1cm should be tested to find out if it is benign or cancerous. This biopsy procedure may be easily done by an experienced radiologist or endocrinologist in the clinic. Using ultrasound to locate the nodule, a very thin needle is inserted into the nodule to draw out cells, which are then spread onto a slide and examined under a microscope. This procedure is known as fine needle aspiration (FNA). No anaesthesia is needed as the patient will only experience minor discomfort, very little bleeding and mild bruising at most. The whole procedure should be completed within a few minutes. The biopsy is classed into 6 categories (the Bethesda system) ranging from benign to cancerous. Should the result be uncertain, the FNA should be repeated. Nodules that are benign do not need to be removed, only checked yearly with an ultrasound and possibly an FNA to check for any changes. The possibility of a benign nodule becoming cancerous is very low.