Diagnosis and Prognosis of Thyroid Cancer
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The diagnosis and prognosis of thyroid cancer includes the following:
- ]]>Review of medical history]]>
- ]]>Physical exam]]>
- ]]>Diagnostic testing]]>
Review of Medical History
If your doctor is suspicious that you may have thyroid cancer, he or she will ask you about your symptoms. Your doctor will also ask about the details of your personal and family medical history. Factors that will stand out as possible risks for thyroid cancer include exposure to radiation in the neck or chest, as well as a personal or family history of thyroid cancer, other endocrine cancers, colon polyps]]> , iodine deficiency, or goiter.
Your healthcare provider will perform a complete physical examination, with special attention paid to your neck. He or she will check to see if you have any visible swelling in your neck, or whether he or she can feel any lumps or nodules. Your neck will be checked for enlarged lymph nodes. You’ll be asked to take a drink of water, while your healthcare provider watches carefully—a thyroid nodule may become more apparent during swallowing.
- Calcitonin—best blood test for medullary cancer
- Thyroglobulin—best blood test for papillary and follicular cancers
- PET proto-oncogene—test for those with known or suspected medullary cancer
Although blood tests are often ordered, they won’t definitively diagnose thyroid cancer. Thyroid scans may identify the presence of nodules, but can’t distinguish between benign growths and malignancies. Although ultrasound can identify the presence of a mass and can help distinguish a cystic mass (fluid-filled) from a solid mass, ultrasound alone can’t actually diagnose thyroid cancer. Thyroid cancer must be diagnosed by obtaining a sample of the thyroid gland ( biopsy]]> ) and checking for cancer cells under a microscope.
The thyroid tissue sample can be obtained with fine needle aspiration (FNA), which involves putting a tiny, thin needle into the thyroid and withdrawing a sample. The cells obtained are examined under a microscope in order to identify the presence of cancer cells. Ultrasound examination of the thyroid may be done in order to guide the placement of the needle for FNA. Ultrasound is the use of sound waves and the characteristic patterns they make bouncing off of various structures in the body to identify tumors and other conditions.
In the rare instances when ]]>fine needle aspiration]]> fails to provide cells for diagnosis, open biopsy of the thyroid gland can be performed. This involves making an incision in the neck, opening up the area around the thyroid, and removing a sample of thyroid tissue for examination under a microscope.
Cytology is the study of cells. The cytology of cancer cells differs significantly from normal cells, and physicians use the unique cellular features seen on biopsy samples to determine the diagnosis and assess the prognosis of a cancer.
The first thing that cytology studies will do is determine what type of thyroid cell the cancer involves, for example, follicular, papillary, anaplastic, or medullary. Cytology will also try to determine the degree of abnormality and aggressiveness of the cancer cells.
Staging is the process by which physicians determine the prognosis of a cancer that has already been diagnosed. Staging is essential for making treatment decisions (eg, surgery vs. chemotherapy]]> ). Several features of the cancer are used to arrive at a staging classification, the most common being the size of the original tumor, extent of local invasion, and spread to distant sites (metastasis). Low staging classifications (0-1) imply a favorable prognosis, whereas high staging classifications (4-5) imply an unfavorable prognosis.
Information to aid in staging thyroid cancer can come from the results of imaging studies, such as:
- CT scan—This is a type of x-ray that uses a computer to produce cross-sectional images of the inside of the body.
- ]]>MRI scan]]> —This test uses magnetic waves to produce images of the inside of the body. Using a large magnet, radio waves, and a computer, an MRI produces 2D and 3D pictures.
- Radioactive iodine uptake (RAIU) test – A radioactive substance called a tracer (usually iodine or technetium) is taken in either a liquid or capsule. It is absorbed by the thyroid gland from the bloodstream. Then, a special probe measures the amount of radioactive substance absorbed by the thyroid gland. The amount of uptake can help diagnose thyroid abnormalities.
- Radioactive octreotide scan—A radioactively tagged hormone called somatostatin is given. This hormone attaches to certain tumors because—compared with normal, noncancerous tissue—many neuroendocrine tumors have much higher concentrations of somatostatin receptors. After the hormone is given, a special machine is used to recognize the radioisotope and produce a hot spot where the tumor is located.
TNM Staging of Thyroid Cancer
Once all the information has been collected, your doctor will determine the stage of your cancer. A common system used for staging is called the TNM system. This system characterizes three aspects of thyroid cancer: information about the tumor (T), the lymph nodes (N), and the presence of distant metastasis (M). As with grading, the higher numbers reflect a greater degree of abnormality and spread.
Tumor (T) Stage
The T stages are as follows:
- TX: Tumor cannot be evaluated.
- T0: There is no evidence of tumor.
- T1: Thyroid tumor is 2 centimeters (cm) or less.
- T2: Thyroid tumor is 2 cm to 4 cm, and within the thyroid.
- T3: The thyroid tumor is larger than 4 cm and within the thyroid, or any tumor that has minimal extension outside of the thyroid.
The thyroid tumor has spread beyond the thyroid and involves other neighboring tissues within the neck. All anaplastic thyroid cancers are considered T4 tumors. Tumors may be divided to T4a and T4b.
- T4a: This refers to a thyroid tumor regardless of size, which extends beyond the capsule surrounding the thyroid gland invading the esophagus, trachea, and larynx .
- T4b: The thyroid tumor invades blood vessels (the carotid artery or blood vessels in chest) and the covering around the vertebrae.
Note: All anaplastic thyroid cancers are considered T4 tumors, with T4a being surgically resectable and T4b being surgically unresectable.
Lymph Nodes (N) Stage
The N stages are as follows:
- NX: Nodes cannot be evaluated.
- N0: There are no cancer cells in the regional lymph nodes.
- N1: There are cancer cells in lymph nodes of the neck (cervical lymph nodes) or upper chest (upper mediastinal lymph nodes). N1 nodes may be divided to N1a and N1b, depending on the distance from the thyroid.
Distant Metastasis (M) Stages
The M stages are as follows:
- MX: Presence of metastasis cannot be evaluated.
- M0: There is no distant metastasis.
- M1: There is distant metastasis, such as to distant lymph nodes, liver, lungs, and/or brain.
Once the cell type and T, N, and M categories have been determined, the information is grouped together to determine your stage. Staging of follicular and papillary thyroid cancers also takes into account your age, since the disease has a higher mortality rate in people over the age of 45. The groupings are explained here.
Staging for Follicular or Papillary Thyroid Cancer
Stage I: T1, N0, M0
Stage II: T2, N0, M0
- T3, N0, M0
- T1-3, N1a, M0
- T4a, N0-N1a, M0
- T1-4a, N1, M0
- T4b, any N, M0
- T1-4, any N, M1
Staging for Medullary Thyroid Cancer
Stage I: T1, N0, M0
Stage II: T2, N0, M0
Stage III: T1-3, N1a, M0
Stage IV: Any T, any N, M1
Staging for Anaplastic Thyroid Cancer
All anaplastic thyroid cancers are considered to be Stage IV because of the aggressive, fast-growing nature of the disease. Stage IV is made up of any T, any N, and any M.
Prognosis is a forecast of the probable course and/or outcome of a disease or condition. Prognosis is most often expressed as the percentage of patients who are expected to survive over five or ten years. Cancer prognosis is a notoriously inexact process. This is because the predictions are based on the experience of large groups of patients suffering from cancers at various stages. Using this information to predict the future of an individual patient is always imperfect and often flawed, but it is the only method available.
If you develop thyroid cancer, your prognosis will depend on your age, sex, the size of the thyroid cancer, and whether the cancer has spread to neighboring structures and/or distant organs. Caught early, thyroid cancer is very treatable, and survival rates are almost 100%.
Prognosis by Stage
The five-year survival rates after treatment for each stage and type of thyroid cancer are as follows:
Follicular thyroid cancer: 99%
Papillary thyroid cancer: 100%
Medullary thyroid cancer: 100%
Follicular thyroid cancer: 99%
Papillary thyroid cancer: 100%
Medullary thyroid cancer: 97%
Follicular thyroid cancer: 79%
Papillary thyroid cancer: 96%
Medullary thyroid cancer: 78%
Follicular thyroid cancer: 45%
Papillary thyroid cancer: 48%
Medullary thyroid cancer: 24%
Anaplastic thyroid cancer: 9%
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Last reviewed June 2007 by ]]>David Juan, MD]]>
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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