Thyroid Nodule
Thyroid Nodule: Excerpt from The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
Stephen F. Wheeler and David E. Bybee
Palpable nodules are present in 4% to 7% of adults. Prevalence is four to nine times greater in women than men. Approximately 5% of all solitary nodules are carcinomas.
Approach
The evaluation of nodular thyroid disease focuses on the functional status of the gland and detection of clinically significant cancer.
A. Functional status. Thyroid function is evaluated through history, physical examination, and appropriate testing (Chapters 14.4 and 14.8).
B. Cancer risk. Prior radiation exposure increases the rate of development of both benign and malignant new nodules by approximately 2% per year. Peak incidence is 15 to 25 years after exposure. Because similar frequencies of cancer have been found in glands having solitary or multiple nodules on palpation, consider dominant nodules in multinodular thyroids for diagnostic evaluation (1). Age less than 20 or more than 60 years and male gender are also commonly cited risk factors for thyroid cancer.
History
Although history is neither sensitive nor specific for diagnosing thyroid cancer, an appropriately focused history can significantly alter the clinical likelihood of malignancy (2).
A. Family history. Approximately 3% of cases of papillary cancer are familial and a high incidence has been reported in patients with adenomatous polyposis coli (Gardner’s syndrome). Medullary cancer often occurs in a hereditary pattern.
B. Personal history. Recent increase in size of a nodule, hoarseness, dysphagia, stridor, or dyspnea can indicate growth or invasiveness and increase the suspicion of cancer. Recurrence of cystic nodules after aspiration is also suggestive of cancer.
1. External beam irradiation before the age of 15 to 20 years, which has been done for conditions such as acne and thymic or tonsillar enlargement, or exposure to ionizing radiation from a nuclear accident, increases the risk of thyroid carcinoma. The risk increases for 15 to 25 years after exposure, remains maximal and stable for 20 years, and then slowly declines.
2. Sudden onset of localized swelling, pain, or tenderness suggests hemorrhage into a preexisting nodule or cyst. Subacute thyroiditis is suggested by fever, a preceding viral illness, and a gradual onset of swelling, pain, and tenderness. Typical symptoms of hypothyroidism suggests Hashimoto’s thyroiditis, whereas thyrotoxicosis suggests toxic adenoma or toxic multinodular goiter (3).
Physical examination
As with the history, physical examination is neither sensitive nor specific for malignancy.
A. General examination. Look for typical vital and physical signs consistent with hypothyroidism or thyrotoxicosis.
B. Thyroid examination. Inspect the neck below the thyroid cartilage from the front and side, using cross-lighting to accentuate shadows and masses. Full extension of the neck enhances visibility of the gland. During palpation, approach the patient from either the front or behind and palpate using the fingers or thumbs. Having the patient swallow during both inspection and palpation causes the thyroid to move and aids in developing a three-dimensional impression of the gland. Note the location, size, consistency, mobility, and tenderness of all nodules. Findings suggestive of cancer include a nodule that is hard, irregular, nontender, greater than 4 cm in size, fixed to surrounding structures or associated with local lymphadenopathy.
Testing
A. Laboratory testing. Serum thyroid-stimulating hormone, performed by a sensitive method (sTSH), should be assessed in every patient. It is the best screen for both hypothyroidism (elevated sTSH—Chapter 14.4) and thyrotoxicosis (suppressed sTSH—Chapter 14.8). A family history of medullary thyroid cancer or multiple endocrine neoplasia, type II, warrants a basal serum calcitonin (4).
B. Diagnostic imaging. Because diagnostic imaging cannot reliably differentiate benign from malignant nodules, it is not part of the routine assessment of thyroid nodules. Diagnostic imaging, however, may be helpful in certain circumstances. Ultrasonography can be useful when findings on palpation are inconclusive regarding the presence of a single nodule or a dominant nodule in a multinodular gland (5). Some clinicians also apply ultrasonography when an abnormality has been detected fortuitously by other imaging procedures or in patients with a history of head and neck irradiation (1). A radionuclide scan, usually done with 123I, can also be helpful when thyroid palpation is inconclusive or to differentiate the functional status of nodules in a multinodular gland. A nodule identified as hyperfunctioning by radionuclide scan is almost invariably benign, but such lesions constitute less than 10% of all nodules.
C. Fine-needle aspiration biopsy (FNAB), performed and interpreted by experienced individuals, is the most important test in the evaluation of thyroid nodules. In various studies, FNAB has demonstrated a sensitivity of 68% to 98% (mean, 83%) and specificity of 72% to 100% (mean, 92%). Use of FNAB has allowed many centers to increase the yield of thyroid cancer in excised nodules from 15% to 45% (2).
Diagnostic assessment
When the initial examination is suggestive of cancer, an immediate surgical consultation is appropriate. In all other patients, FNAB is the cornerstone in the evaluation of solitary or dominant thyroid nodules.
A. Management strategy. The cytopathologic interpretation of the FNAB dictates management. If the specimen is insufficient for diagnosis, repeat FNAB is necessary. Even in experienced hands, approximately 10% of biopsies are nondiagnostic (1). If the biopsy is clearly benign, periodic follow-up is necessary. If the biopsy is malignant, suspicious, or indeterminate, surgical consultation is warranted.
B. Follow-up. During follow-up of nodules not surgically explored, the significant historical and physical elements previously discussed should be reexamined. Although the intervals of follow-up will vary, based on patient and nodule characteristics, a standard protocol is to reexamine patients at intervals of 1.5, 3, 6, and 12 months, and then annually if the nodule is stable. Consider the judicious use of laboratory testing, diagnostic imaging, and repeat FNAB, again based on patient and nodule characteristics. Thyroid hormone suppression is commonly used in both the diagnosis and treatment of thyroid nodules. Recent controlled trials have raised questions about this practice. If suppressive therapy is considered, the risks associated with subclinical hyperthyroidism must be included in the risk-to-benefit analysis (2).
References
1. Singer PA, Cooper DS, Daniels GH, et al. Treatment guidelines for patients with thyroid nodules and well-differentiated thyroid cancer. Arch Intern Med 1996;156:
2165–2172.
2. Thyroid Nodule Task Force of the American Association of Clinical Endocrinologists and the American College of Endocrinology. AACE Clinical Practice Guidelines for the Diagnosis and Management of Thyroid Nodules. Endocrine Prac 1996;2:78–84.
3. Petrone LR. A primary care approach to the adult patient with nodular thyroid disease. Arch Fam Med 1996;5:92–100.
4. Mazzaferri EL. Management of a solitary thyroid nodule. N Engl J Med 1993;328:
553–559.
5. Tan GH, Gharib H. Solitary thyroid nodule: comparison between palpation and ultrasonography. Arch Intern Med 1995;155:2418–2423.
Book Source Details
- Book Title: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter
- Author(s): Robert B. Taylor (editor)
- Year of Publication: 2000
- Copyright Details: The 10-Minute Diagnosis Manual: Symptoms and Signs in the Time-Limited Encounter, Copyright © 2000 Lippincott Williams & Wilkins.
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Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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