Thyroid Cancer
Clinical OncologyOtolaryngologyGeneral SurgeryEndocrinology, Diabetes and Metabolism
In 2020, there were a total of 978 new cases of thyroid cancer, accounting for 2.9% of all new cancer cases in Hong Kong and ranking tenth among common cancers. The incidence rate per 100,000 population is approximately 13 cases. Thyroid cancer patients are typically middle-aged to elderly, with papillary thyroid cancer occurring in younger people and rare in children. Additionally, the risk of thyroid cancer is higher in females, with a rate approximately 3.8 times that of males.
The development of thyroid cancer is generally slow, and it may take several years, from the formation of cancer cells to the appearance of symptoms. However, modern medical technology allows for detecting even small thyroid tumours, and new treatment methods have increased the cure rate. Nevertheless, due to its slow progression, there is a risk of recurrence many years after successfully treating thyroid cancer. Therefore, patients need to undergo regular follow-up examinations.
Symptoms
The thyroid is located in the front of the neck, just below the larynx, and has a butterfly-like shape. It is an endocrine organ responsible for secreting thyroid hormones. Behind the thyroid are the parathyroid glands, which secrete parathyroid hormones. Thyroid hormones regulate metabolism, blood sugar, heart rate, and kidney function, among other things. In contrast, parathyroid hormones regulate calcium levels in the body, maintain calcium balance in bones, and promote calcium absorption in the small intestine and kidneys. When the thyroid cells undergo uncontrolled, abnormal growth, it can lead to thyroid cancer.
Symptoms of thyroid cancer include:
- Painless lump in the neck
- Persistent hoarseness
- Neck or throat pain
- Difficulty swallowing or breathing with a feeling of constriction
- Persistent cough
- Unexplained weight loss
The medical community has not yet definitively identified the causes of thyroid cancer, but it may be associated with the following risk factors:
- Exposure to High Levels of Radiation
For example, having received head and neck X-ray radiation or radiation therapy during childhood or living in an environment with high radiation levels. In areas with radiation leaks from foreign nuclear power plants, the incidence of thyroid cancer is notably higher.
- Family History
A family history of thyroid tumours, familial medullary thyroid cancer, multiple endocrine neoplasia, or hereditary colon polyps increases the likelihood of developing thyroid cancer.
- Personal Medical History
Personal history of thyroid tumours or benign thyroid nodules raises the risk of developing thyroid cancer.
- Diet
A diet lacking in iodine may also increase the risk of developing thyroid cancer.
- Age
Thyroid cancer is more common in individuals over the age of 40.
- Gender
Women are at a higher risk of developing thyroid cancer compared to men.
Diagnosis
Diagnostic methods for thyroid cancer include:
| Palpation | Doctors will use their fingers to touch the patient's neck to examine the thyroid and lymph nodes for abnormalities. |
| Blood Tests | These tests can be used to assess the patient's overall health and check if thyroid hormone levels are within the normal range. |
| Fine Needle Aspiration (FNA) Biopsy | A fine needle is inserted into a neck lump to extract cells, which are then examined under a microscope to check for cancerous cells. Doctors may use ultrasound scans to guide the placement of the fine needle. |
| Surgical Biopsy | If FNA doesn't yield enough tissue for examination, the doctor may need to perform a surgical procedure to extract a tissue sample. The doctor will make a small incision in the skin near the thyroid, then take a small piece of thyroid tissue for examination under a microscope to check for cancerous cells. |
| Ultrasound Scans | Doctors use ultrasound to create images of the neck and the inside of the thyroid, allowing them to visualize whether the tissues are solid masses or fluid-filled cysts. |
| Thyroid Radioactive Isotope Scanning | Doctors use ultrasound to create images of the neck and the inside of the thyroid, allowing them to visualize whether the tissues are solid masses or fluid-filled cysts. |
| CT Scan: | A computer takes and processes a series of X-ray images to create three-dimensional images, providing detailed information about the size and location of tumours and other structures. Patients may need to ingest a special contrast dye for this examination. |
In Hong Kong, up to 90% of thyroid cancers belong to well-differentiated and favourable prognostic categories, which include papillary and follicular types.
| Type | Commonality | Affected Population |
|---|---|---|
| Papillary Carcinoma | Most common | Young women |
| Follicular Carcinoma | Less common | Elderly |
| Medullary Carcinoma | Rare | Associated with a family history of hereditary cancers |
| Anaplastic Carcinoma | Rare | Elderly |
Staging of Thyroid Cancer
| Stage | Below 45 Years | Above 45 Years |
|---|---|---|
| Stage I | - Any tumour size - Or regional lymph node involvement - No distant organ metastasis | - Tumour size is under 2 cm - No regional lymph node involvement - No distant organ metastasis |
| Stage II | - Any tumour size - Or regional lymph node involvement - Distant organ metastasis present | - Tumour size ranges from 2 to 4 cm - No regional lymph node involvement - No distant organ metastasis |
| Stage III | - Tumour extending beyond the thyroid gland - Or regional lymph node involvement present | - Tumour extending beyond the thyroid gland - Or regional lymph node involvement present |
| Stage IV | - Tumour extending into nearby trachea or oesophagus - Distant organ metastasis present | - Tumour extending into nearby trachea or oesophagus - Distant organ metastasis present |
| Surgical Treatment | Surgery is the primary treatment for thyroid cancer. The doctor will examine nearby lymph nodes for any involvement by cancer cells. If cancer cells have spread beyond the thyroid, the doctor may remove the tissues near the thyroid. After the complete or near-complete removal of the thyroid, patients will need to take thyroid hormone replacement for life to replace the hormones no longer produced by the thyroid. |
| Radioactive Iodine Treatment | If surgery does not completely clear the cancer cells, or if there are indications of metastasis or spread, patients may require radioactive iodine treatment. It is an internal radiation therapy where radioactive iodine is administered to the patient in capsules or liquid. Thyroid cancer cells absorb radioactive iodine, which destroys them, while normal cells are minimally affected. |
| External Beam Radiation Therapy | If there are residual cancer cells in the neck after surgery or the tumour cannot be entirely removed by surgery, the doctor may consider using external beam radiation therapy. This method is more commonly used for treating medullary and anaplastic carcinomas. It may also be considered if cancer recurs. |
| Targeted Therapy | When standard treatments like surgery and radioactive iodine become ineffective, targeted therapy drugs may be considered. |
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