Thyroid cancer is cancer that arises from the thyroid gland. It is more common in women than men. In Singapore, it is the 9th most common cancer diagnosed in women. It is commonly diagnosed at a younger age than most other cancers and most cases occur in patients less than 60 years old. The incidence of thyroid cancer appears to be rising, but this appears to be mostly due to the increased use of ultrasound scanning, picking up more thyroid nodules that may not have been discovered in the past.

What kinds of thyroid cancer are there?

There are many types of thyroid cancers.

Differentiated Thyroid Cancers

1. Papillary Thyroid Cancer

This is the most common kind of thyroid cancer seen, accounting for about 75% of thyroid cancers. Papillary thyroid cancers usually are slow growing but they have a tendency to spread to the lymph nodes in the neck. However, most of these cancers can still be treated successfully.

There are many subtypes of papillary thyroid cancer. Some less common subtypes (follicular variant, tall cell, insular, diffuse sclerosing) tend to have more aggressive behaviour and may grow and spread more quickly.

2. Follicular Thyroid Cancer

Follicular thyroid cancer is the second most common type of thyroid cancer seen, accounting for about 15% of cases. These cases tend to spread via the bloodstream to other parts of the body such as the lungs and bones.

Other types of Thyroid Cancers

3. Medullary Thyroid Cancer

Medullary thyroid cancer is much less common and accounts for about 5% of thyroid cancers. These cancers arise from the parafollicular C cells in the thyroid gland. These cells usually are responsible for producing a hormone called calcitonin, which helps to control the level of calcium in the body.

About 20% of these cases are hereditary (familial medullary carcinoma). Patients with familial medullary thyroid carcinoma tend to develop thyroid cancers at an earlier age in childhood and may also develop other types of cancers (e.g. phaeochromocytoma, parathyroid tumours).

Although the outcome of treatment for medullary thyroid cancer is not as good as for papillary and follicular thyroid cancers, many patients can still be treated successfully.

4. Anaplastic Thyroid Cancers

This type of cancer accounts for about 2% of thyroid cancers. These cancers tend to be very aggressive tumours and grow very quickly and spread rapidly to other parts of the body. Treatment of these cancers is usually very difficult.

5. Thyroid Lymphoma

This is a very rare cancer that sometimes develops in the thyroid gland. Lymphoma is a type of cancer that arises from white blood cells. These cancers are usually treated with chemotherapy, with or without radiotherapy.