Click here for Frequently Asked Questions on Thyroid Cancer.
Thyroid cancer generally presents as a nodule, lump, or mass in the thyroid. Less commonly, a swollen gland or lymph node in the neck may be the initial manifestation of the disease.
There are several different types of thyroid cancer, with the two most common diseases being papillary and follicular carcinoma of the thyroid, also referred to as well differentiated thyroid cancer. These forms of thyroid cancer occur more commonly in women, are usually not genetic and rarely run in families (less than 10% of the time).
Papillary and follicular thyroid cancers are frequently slow growing and usually have an excellent prognosis, especially if the disease is confined to the neck region. Less common types of thyroid cancer include medullary carcinoma, anaplastic carcinoma, and thyroid lymphoma. The vast majority of thyroid cancers do not have a known genetic basis and arise sporadically. Rarely, well-differentiated thyroid cancers will cluster in families although the genes responsible for familial papillary or follicular carcinoma have not been identified. For an overview of the diagnosis and treatment of all types of thyroid cancers, see Papillary thyroid cancer. Curr Treat Options Oncol. 2006 Jul;7(4):309-19. and Management of thyroid cancer Lancet Oncol 2002 Jul;3(7):407-14.
The most common approach to the diagnosis of thyroid cancer in a patient with a thyroid nodule or 'lump' in the neck is the use of Fine Needle Aspiration Biopsy (FNAB). A range of results may be obtained using FNAB, ranging from normal thyroid cells, to specimens diagnostic for thyroid cancer. Biopsy results that are highly suspicious or diagnostic for thyroid cancer, in the correct clinical context, usually lead to surgical excision of the suspicious lesion or nodule, and often the entire thyroid gland may be removed at the time of surgery. Nevertheless, it is common for biopsy results to be non-diagnostic, either due to limitations in the number of cells obtained, or due to difficulty in making an accurate diagnosis for some types of thyroid pathology. This is often frustrating for patients, who logically assume that the biopsy results should ideally be 100% accurate in making the diagnosis of thyroid cancer.
If biopsies are non-diagnostic, options range from careful follow-up and periodic repeat assessment to repeat biopsy, to surgical excision, depending on the clinical context. Blood tests such as the thyroglobulin level alone are not sufficient for the diagnosis of thyroid cancer. Similarly, a thyroid scan, MRI, CT scan, PET scan or thyroid ultrasound cannot provide a definitive diagnosis of thyroid cancer
With certain types of thyroid nodules, such as follicular adenomas, it may be impossible to differentiate between a benign adenoma or a follicular cancer based on cytology alone, (see FNAB)and surgical excision may be required for accurate diagnosis. If the clinical scenario raises the possibility of medullary thyroid carcinoma (MTC), a calcitonin blood test, genetic testing, or analysis of a biopsy specimen for calcitonin production by histochemical staining, may be useful.
The principal factor identified as increasing the risk of developing thyroid cancer is a history of exposure to ionizing radiation (often in the form of X-Rays). The majority of patients however, have no history of radiation exposure.
- Why did I get thyroid cancer?
- Psychological Impact of a thyroid cancer diagnosis
- Treatment of Thyroid Cancer
- Thyroid surgery
- Radioactive iodine
- Follow-up for patients with thyroid cancer
For a more detailed overview of thyroid cancer, see the NIH CancerNet Web site. To review a representative set of detailed guidelines for the treatment of thyroid cancer, see the document published by experts representing the National Comprehensive Cancer Network on Thyroid Cancer. Also see the American Thyroid Association Guidelines for the Diagnosis and Management of Thyroid Cancer Revised American Thyroid Association Management Guidelines for Patients with Thyroid Nodules and Differentiated Thyroid Cancer November 2009
The vast majority of patients with well differentiated papillary and follicular thyroid cancer have an excellent prognosis and the thyroid cancer will frequently not contribute to morbidity and mortality in most patients. Nevertheless, the diagnosis is often a shock, and can produce some degree of psychological distress and anxiety. Patients with small tumors less than 4 cm, confined to the neck, generally do extremely well, with 20 year survival rates in excess of 90%. Furthermore, with the advent of improved diagnostic techniques, many tumors are diagnosed when they are quite small, and the likelihood of disease-free survival may be even greater than is stated in current published statistics, which reflect thyroid cancer diagnosis and treatment 10-30 years ago. Analysis of serial trends in thyroid cancer diagnosis confirms that the majority of well differentiated thyroid cancers diagnosed today are smaller than they were several decades ago Trend in thyroid carcinoma size, age at diagnosis, and histology in a retrospective study of 500 cases diagnosed over 20 years. Thyroid. 2006 Nov;16(11):1151-5
For an example of some recent data, see Oncology 2000 May;58(4):280-285. or Papillary thyroid carcinoma: prognostic factors and the role of radioiodine and external radiotherapy. Int J Radiat Oncol Biol Phys. 2002 Mar 1;52(3):784-795 and Prognostic factors determining long-term survival in well-differentiated thyroid cancer: an analysis of four hundred eighty-four patients undergoing therapy and aftercare at the same institution. Thyroid. 2003 Oct;13(10):949-58. For recent Canadian Registry statistics, see Cancer Statistics 2000 database.
Some retrospective studies have stratified patients into low risk and high risk categories. Subset analyses reveals that 20 year survival of low risk patients may be as high as 98%. In a retrospective analysis done at the Lahey clinic using the AMES prognostic criteria, 585 patients (80.5%) were defined as low-risk patients and 142 (19.5%) as high-risk patients. Overall 20-year survival for the low-risk group was 97.8%, and that of the entire high-risk group was 61.3%. The definitions used to stratify patients were: The low-risk group = women younger than 51 years and men younger than 41 years with no distant metastasis. Also included in this group were older patients with favorable tumors smaller than 5 cm and no extrathyroidal extension of tumor. The high-risk patient group included all patients with metastatic disease, women aged 51 years or older, and men aged 41 years and older with tumors greater than or equal to 5 cm or with extrathyroidal extension. Survival for low risk patients did not appear to be affected by extent of surgery, performance of a lymph node dissection, or the use of radioactive iodine. For more details, see Predicting outcome and directing therapy for papillary thyroid carcinoma. Arch Surg. 2004 Apr;139(4):390-4; discussion 393-4.
My pathology report showed follicular variant of papillary thyroid cancer-how does this differ from regular papillary thyroid cancer?
The two most common types of well differentiated thyroid cancer are papillary and follicular cancer. Very commonly, when the tumor is examined under the microscopic, there are mixed features of different cell types seen, with elements of both papillary and follicular tumor types seen in the same tumor. There is little evidence that mixed follicular variant papillary cancer carries a significantly different connotation compared to simple papillary thyroid cancer. See Pure versus follicular variant of papillary thyroid carcinoma. Cancer. 2003 Mar 1;97(5):1181-5. and Follicular Variant of Papillary Thyroid Carcinoma: A Comparative Study of Histopathologic Features and Cytology Resutls in 141 Patients. Endocr Pract. 2001 Mar;7(2):79-84. However in some studies, the behavior of this type of tumor may be slightly more aggressive compared to PTC alone Follicular variant of papillary thyroid carcinoma: clinical-pathological characterization and long-term follow-up. Cancer J. 2006 Jul-Aug;12(4):275-82.
How often do I need to have a total body scan for follow-up of my thyroid cancer?
The frequency of follow-up scans varies depending on the type of thyroid cancer, the size of the initial cancer, the serum thyroglobulin, and findings from history and clinical examination. In many centers, if the neck examination is unremarkable, and the thyroglobulin is undetectable, an annual scan is no longer a routine test. Patients should review these issues, with particular reference to their own situation, with their physician. Recent studies demonstrate that the diagnostic utility of a routine follow-up total body scan after the initial radioactive iodine treatment is very low and provides little useful clinical information-See J Clin Endocrinol Metab 2000 Jan;85(1):175-8 Is diagnostic iodine-131 scanning useful after total thyroid ablation for differentiated thyroid cancer? An abnormal thyroglobulin level appears to provide more useful information for prediction of disease recurrence. For more information, see Follow-up for patients with thyroid cancer.
I am worried about osteoporosis and my levels of thyroid hormone are quite high. What can I do?
It is important to keep the TSH level suppressed for optimal management of thyroid cancer. There is very good scientific data showing that survival in patients with thyroid cancer is improved if the TSH level is kept suppressed. Most endocrinologists will ensure that patients are on the lowest dose possible of thyroxine required to keep the TSH level suppressed. Bone density may be followed if indicated clinically, and if osteoporosis becomes evident, then appropriate assessment (history, diet, exercise, other risk factors) and treatment may be indicated. It is important to remember that elevated levels of thyroid hormones do not invariably lead to osteoporosis. There are many risk factors for osteoporosis, and many patients with thyroid cancer on suppressive doses of thyroxine have no evidence of osteoporosis. There is no uniformly agreed upon range for TSH and thyroid hormone levels. Patients with a history of more aggressive/extensive thyroid cancer will likely be maintained on thyoxine levels with a goal of keeping the TSH levels undetectable or close to the lower limit of normal. Patients with smaller thyroid cancers who likely have very low risks of disease recurrence may find recommended levels of TSH close to the lower limit of normal, but not frankly suppressed. Patients are reminded that recommendations for precise thyroxine dosing are based on physician recommendations, but not on results on long term, outcome-based randomized clinical trials. The levels of TSH suppression and optimal thyroid hormone dosing will also depend on the patients age, and associated risk factors for both bone disease and heart disease. See Benefits of thyrotropin suppression versus the risks of adverse effects in differentiated thyroid cancer Thyroid. 2010 Feb;20(2):135-46 for a discussion of this issue.
I know several individuals with thyroid cancer? Is the disease becoming more common?
The reported incidence of thyroid cancer seems to be increasing slowly in North America. This may reflect an increase in the true incidence of the disease, and possibly, an increase in the detection rate due to more common use of ultrasounds and related diagnostic imaging studies. The form of thyroid cancer that is increasing in incidence is papillary cancer of the thyroid, as illustrated in Ann Epidemiol 2000 Jan;10(1):24-30 Primary malignancies of the thyroid: epidemiologic analysis of the Florida Cancer Data System registry and Temporal trends for thyroid carcinoma in Australia: an increasing incidence of papillary thyroid carcinoma (1982-1997). Thyroid. 2002 Feb;12(2):141-9. Although many thyroid cancer specialists feel that increased detection of small tumors accounts for much of the increase in thyroid cancer incidence, some studies also report increased rates of large tumors greater than 4 cm in size Increasing incidence of differentiated thyroid cancer in the United States, 1988-2005 Cancer. 2009 Jul 13. [Epub ahead of print]. Consistent with these findings, a review of incidence trends of thyroid cancer diagnosed in the United States over the past several decades reveals a striking shift in the size of thyroid cancers at diagnosis, with microcarcinomas less than 1 cm in size now increasingly common The Most Commonly Occurring Papillary Thyroid Cancer in the United States Is Now a Microcarcinoma in a Patient Older Than 45 Years Thyroid. 2011 Jan 26. [Epub ahead of print] Similarly, a study of thyroid cancer in 4,187 patients from Italy revealed a trend towards smaller tumors, less aggressive features, and better prognosis/survival, in patients diagnosed in the years since 1990, compared to patients diagnosed before 1990 Are the clinical and pathological features of differentiated thyroid carcinoma really changed over the last 35 years? Study on 4187 patients from a single Italian institution to answer this question J Clin Endocrinol Metab. 2010 Apr;95(4):1516-27.
Should I see a thyroid cancer specialist for treatment of my disease?
For most diseases, it is usually preferable to have medical care localized to a site with a large volume of experience in looking after the specific disease and its associated complications. Even in respected university teaching centers, deficiencies in management of thyroid cancer patients may be detected in up to 20% of cases audited. For one scientific study of this issue, see An audit of management of differentiated thyroid cancer in specialist and non-specialist clinic settings. Clin Endocrinol (Oxf). 2001 Jun;54(6):719-23.