Medullary Thyroid Cancer

Medullary thyroid cancer is a rare type of thyroid cancer that arises not from the hormone-producing follicular cells of the thyroid but from the C cells (parafollicular cells), which secrete a hormone called calcitonin. It behaves differently from the other thyroid cancers: it does not respond to radioactive iodine treatment, some cases run in families, and treatment is based on surgery.

What is medullary thyroid cancer?

C cells produce the hormone calcitonin, which is involved in calcium balance; because a tumour arising from these cells also secretes calcitonin, the calcitonin level measured in the blood is a valuable marker both in diagnosis and in follow-up. The disease occurs in two forms:

• Sporadic form: Accounts for most cases; it usually appears as a single nodule in middle to older age.
• Familial (hereditary) form: Passed from parent to child through a change in a particular gene. It may occur on its own or as part of the multiple endocrine neoplasia syndromes, which also affect the adrenal and parathyroid glands. In this form the tumour usually develops in both lobes and at a younger age.

Because of the existence of the familial form, genetic testing is recommended for every patient diagnosed with medullary cancer; if a gene change is found, family members are tested as well, and preventive surgery may be considered for carriers.

Symptoms

• A firm nodule at the front of the neck
• Enlarged lymph nodes in the neck; common at the time of diagnosis
• In advanced disease, hoarseness and difficulty swallowing
• Diarrhoea or facial flushing caused by substances secreted by the tumour (rare)

Diagnosis

The diagnosis is made by ultrasound and fine-needle aspiration biopsy; if there is doubt, calcitonin staining can be performed on the biopsy sample. Calcitonin and carcinoembryonic antigen (CEA) levels are measured in the blood; the calcitonin level gives an idea of the extent of the disease. Before surgery, a detailed ultrasound scan of the neck and, when needed, computed tomography or magnetic resonance imaging of the chest and abdomen guide the planning. Before the operation, an adrenal gland tumour (phaeochromocytoma) and overactivity of the parathyroid glands must be looked for, because these conditions need to be dealt with before surgery.

Treatment

The main treatment is removal of the whole thyroid gland (total thyroidectomy) together with clearance of the central neck lymph nodes around the gland. If the lymph nodes at the sides of the neck are involved, or if the calcitonin level points to widespread disease, the neck dissection is extended. Because medullary cancer cells do not take up iodine, radioactive iodine treatment has no place in this type; the thyroid hormone medication given after surgery serves only to replace the missing hormone. For disease that cannot be removed surgically or that progresses, targeted drugs and, in selected cases, radiotherapy may be used.

After surgery and follow-up

During follow-up, calcitonin and CEA levels are measured at regular intervals; levels that stay low show that the disease is under control, while a rising trend calls for further investigation. Neck ultrasound and, when needed, other imaging are added to the follow-up. Follow-up continues for life. In the familial form, screening of family members is an important part of treatment.

When should you see a doctor?

If you have a growing nodule or lymph node in your neck, if medullary thyroid cancer or the related endocrine syndromes are known in your family, or if you have noticed a swelling in the neck together with unexplained persistent diarrhoea, it is advisable to see a doctor.