Thyroid cancer: 1999 update.

Abstract

Thyroid nodules are common; it is estimated that approximately 4% to 7% of the adult American population has a palpable thyroid nodule, and autopsy and high-resolution ultrasonography studies suggest that up to 50% of adults may have nodules within their thyroid gland.1,2 In contrast, malignant thyroid nodules are relatively rare; with approximately 17,200 new cases of thyroid cancer reported each year, malignant thyroid nodules represent only 1% of all malignancies and 0.5% of all cancer-related deaths.3,4 Because the overwhelming majority of thyroid nodules are benign, the clinician is faced with the difficult task of trying to identify the small number of patients with malignant nodules, which require surgical treatment, among the large number of patients with benign thyroid nodules. The clinical evaluation of a solitary thyroid nodule initially involves identifying risk factors that may increase the probability that a given nodule is malignant. These characteristics include prior neck irradiation; family history; age; whether or not the nodule is solitary; characteristics of the nodule, including size, consistency, and/or fixation; whether there are any enlarged lymph nodes; hoarseness; and pressure symptoms. Although thyroid function tests are often done, it is unusual for thyroid cancer to cause significant alterations in thyroid function. Other modalities that have been used in differentiating benign nodules from malignant ones include thyroid suppression therapy, cervical ultrasonography, and thyroid scintigraphy. First, thyroid suppression therapy, although frequently used, has not been shown to cause a statistically significant decrease in the size of nodules when compared with placebos in recent studies.5,6 There are also numerous reports of nodules that decreased in size during suppression therapy but subsequently turned out to be malignant.7 Second, cervical ultrasonography can identify extremely small nodules in the range of 1 mm in diameter; however, there are no ultrasonographic criteria that are pathognomonic for malignancy.8 Third, thyroid scintigraphy has been used enthusiastically in the past to differentiate between benign and malignant nodules. If one looks at the scintigraphic characteristics of all nodules, 84.0% are cold (nonfunctioning), 10.5% are warm (having uniform tracer uptake), and 4.0% are hot (hyperfunctioning).9,10 Cancer is present in approximately 16% of cold nodules, 9% of warm nodules, and 4% of hot nodules. Therefore, if a nodule is cold, there is an 87% sensitivity for cancer, but specificity is only 30%. Over the past 10–15 years, fine-needle aspiration (FNA) biopsy has emerged as the most accurate and cost-efficient way to differentiate benign from malignant nodules with an accuracy rate approaching 95%.11 FNA From the Department of Surgery (D.S.T.), Duke University, Durham, North Carolina; Department of Surgery (A.R.S.), Memorial Sloan-Kettering Cancer Center, New York, New York; Department of Surgery (R.A.U.), The Johns Hopkins University, Baltimore, Maryland; Department of Medical Specialties, Endocrinology (S.I.S.) and Department of Surgical Oncology (D.B.E.), The University of Texas M. D. Anderson Cancer Center, Houston, Texas; Department of Surgery (N.W.T.), University of Michigan, Ann Arbor, Michigan; Department of Surgery (J.F.M.), Washington University School of Medicine, St. Louis, Missouri. Received September 21, 1999; accepted November 29, 1999. This report presents summaries from the 52 Annual Cancer Symposium of the Society of Surgical Oncology at Orlando, Florida, March 4–7, 1999. Address correspondence to: Douglas B. Evans, MD, The University of Texas M. D. Anderson Cancer Center, Department of Surgical Oncology, Box 106, 1515 Holcombe Blvd., Houston, TX 77030; Fax: 713-745-4426; E-mail: devans@notes.mdacc.tmc.edu Annals of Surgical Oncology, 7(5):376–398 Published by Lippincott Williams & Wilkins © 2000 The Society of Surgical Oncology, Inc.