This information is about a specific type of non-Hodgkin lymphoma, known as thyroid lymphoma. It should ideally be read with our general information about non-Hodgkin lymphoma.

Occasionally, another type of lymphoma, known as Hodgkin lymphoma, may arise in the thyroid gland.

The thyroid is a small gland in the front of the neck, just below the voice box (larynx), and it is made up of two parts, or lobes. It is one of a network of glands throughout the body that make up the endocrine system. This system is responsible for producing the body’s hormones, which help to control and influence various functions. The thyroid is sometimes known as the 'activity gland' because it produces the two main hormones, thyroxine (T4) and triiodothyronine (T3), which are needed to keep the body functioning at its normal rate. The thyroid gland needs a regular supply of iodine (which is added to table salt and found in fish and dairy products) in order to produce thyroxine.

There are more than 20 different types of non-Hodgkin lymphoma (NHL). Most of them start in the lymphatic system. However, several of them can arise in organs or tissue outside the lymphatic system. When this happens, the lymphoma is described as being extranodal. Thyroid lymphoma is an rare type of extranodal lymphoma.

Thyroid lymphoma is usually a disease of the B-lymphocytes. There are different subtypes of NHL that can affect the thyroid gland. The main subtypes are large cell lymphoma and MALT lymphoma. MALT stands for mucosa associated lymphoid tissue (a specialised type of lymph tissue found in certain parts of the body). MALT lymphoma tends to occur in people in their 60s and 70s, and is usually more common in women than in men. MALT lymphoma is also known as extranodal marginal zone B-cell lymphoma.

There are other, much rarer types of lymphoma that can arise in the thyroid gland, including follicular lymphoma.

Most people develop a lump in the thyroid. This gland is in the middle of the neck near the Adam’s apple. Some people may have a history of Hashimoto’s thyroiditis, which is an inflammatory condition of the thyroid that can be associated with several conditions, including thyroid lymphoma. Some people may have a larger swelling involving the lower neck and may develop a hoarse voice, or difficulty breathing or swallowing.

Thyroid lymphoma can sometimes spread to the lymph nodes nearby. The MALT type can involve the digestive tract. It is not common for thyroid lymphoma to spread to the bone marrow.

Thyroid lymphoma can sometimes be difficult to diagnose, and occasionally it may be mistaken for other types of thyroid cancer. Before a firm diagnosis can be made, a number of tests and investigations may be needed.

Ultrasound thyroid scan This involves using sound waves to make up a picture of the inside of the neck and thyroid. Once you are lying comfortably on your back, a gel is spread over your neck. A small device which produces sound waves is then rubbed over the area. The echoes are changed into a picture by a computer and may show whether the lump is solid or just fluid in a cyst.

Fine needle aspiration cytology A sample may be taken from the thyroid gland, by inserting a small needle into it and drawing out some cells. These cells are then examined to see whether or not cancer is present.

Open biopsy A definite diagnosis is made by doing a biopsy. This involves a small operation to remove a piece of thyroid tissue, whose cells will then be examined under a microscope. Biopsies may also be taken from other body tissues.

Staging

The stage of a cancer is the term used to describe the extent of the cancer: whether it affects the thyroid alone, or has spread elsewhere in the body.

Additional tests, including blood tests, x-rays, scans, and bone marrow samples, are used to get more information about the type of lymphoma, and how far it has spread in the body. This information is used to help decide which treatment is most appropriate for you.

Thyroid lymphoma can spread to the lymph nodes and bone marrow, but this is far less common than in other types of lymphoma. If it has spread to the lymph nodes, the stage refers to how many groups of lymph nodes are affected, where they are in the body, and whether any other organs are affected.

Grading

Non-Hodgkin lymphomas may also be divided into one of two groups: low-grade and high-grade. Low-grade lymphomas are usually slow growing and high-grade lymphomas tend to grow more quickly.

Thyroid lymphoma can be low or high-grade. Sometimes low-grade thyroid lymphomas can change to high-grade. Large cell lymphomas are high-grade and MALT lymphomas tend to be low-grade.

Treatment depends on the subtype of lymphoma and whether or not it is confined to the thyroid.

Low-grade disease that is contained within the thyroid gland, such as MALT thyroid lymphoma, is usually treated with radiotherapy alone. Occasionally, surgery may be used to completely remove the thyroid gland. If the lymphoma has spread or come back after initial treatment, it is often treated with chemotherapy and steroid drugs which are known as CVP (cyclophosphamide, vincristine and prednisolone). There are also trials in progress, combining chlorambucil with rituximab (ri-tucks-i-mab), a monoclonal antibody treatment. Rituximab can also be given alongside CVP.

High-grade disease that is contained within the thyroid gland is usually treated with a short course of chemotherapy (3–4 courses or cycles), followed by radiotherapy. If the disease has spread beyond the thyroid gland, then usually six cycles of chemotherapy are given. Treatment is a combination of chemotherapy drugs called CHOP. This includes the drugs vincristine (vin-chris-teen) and prednisolone (pred-ni-so-lone), as well as doxorubicin (docks-o-ruo-bi-sin) and cyclophosphamide (sigh-clo-fos-fa-mide). The chemotherapy can usually be given as an outpatient at hospital. Rituximab is usually given in combination with the chemotherapy.

Thyroid hormone replacement Often people who have been treated with radiotherapy, or surgery, will need thyroid hormone replacement treatment as the thyroid becomes less active. This involves taking tablets to replace the hormones normally produced by the thyroid.

Steroids are drugs that are often given with chemotherapy to help treat lymphomas. They also help you feel better and can reduce feelings of sickness.

Surgery is not usually used as a treatment to remove a thyroid lymphoma. This is to help preserve the function of the thyroid gland.

Monoclonal antibodies are drugs that recognise, target, and stick to cancer cells. A monoclonal antibody called rituximab (Mabthera®) has been shown to be effective as a treatment for B-cell lymphomas.

New treatments for thyroid lymphoma are being researched all the time, and you might be invited by your doctor to take part in a clinical trial to compare a new treatment against the best available standard treatment. Your doctor must discuss the treatment with you, and have your informed consent before entering you into a clinical trial.

The need for practical and emotional support is individual. For some people with thyroid lymphoma, life may seem largely unaffected; for others the diagnosis of cancer may be a cause of great fear and distress. Should you wish to discuss the condition, its treatment, or the practical and emotional problems of living with thyroid lymphoma, please contact our cancer support service.

This section has been compiled using information from a number of reliable sources, including:

• Oxford Textbook of Oncology (2nd edition). Eds Souhami et al. Oxford University Press, 2002.
• Wintrobe’s Clinical Haematology (11th edition). Eds Lee et al. Williams and Wilkins, 2004.
• Malignant Lymphoma. Eds Hancock et al. Arnold, 2000.
• Full Guidance On Rituximab For Aggressive Non-Hodgkin Lymphoma. National Institute for Clinical Excellence (NICE), September 2003.
• British Committee For Standards In Haematology Guidelines On Nodal Non-Hodgkin Lymphoma. Draft 2, August 2002.

For further references, please see the general bibliography.