Published online before print April 10, 2008, 10.1148/radiol.2473070944
(Radiology 2008;247:762.)
A more recent version of this article appeared on June 1, 2008
© RSNA, 2008
Benign and Malignant Thyroid Nodules: US Differentiation—Multicenter Retrospective Study1
Won-Jin Moon, MD,
So Lyung Jung, MD,
Jeong Hyun Lee, MD,
Dong Gyu Na, MD,
Jung-Hwan Baek, MD,
Young Hen Lee, MD,
Jinna Kim, MD,
Hyun Sook Kim, MD,
Jun Soo Byun, MD, and
Dong Hoon Lee, MD For the Thyroid Study Group, Korean Society of Neuro- and Head and Neck Radiology
1 From the Department of Radiology, Kangbuk Samsung Hospital, Sungkyunkwan University School of Medicine, Seoul, Korea (W.J.M.); Department of Radiology, Konkuk University Hospital, Konkuk University School of Medicine, 4-12, Hwayang-dong, Gwangjin-gu, Seoul 143-914, Korea (W.J.M.); Department of Radiology, Kangnam St Mary's Hospital, Catholic University College of Medicine, Seoul, Korea (S.L.J.); Department of Radiology, Asan Medical Center, Ulsan University College of Medicine, Seoul, Korea (J.H.L.); Department of Radiology, Seoul National University Hospital, Seoul National University, Seoul, Korea (D.G.N., D.H.L.); Department of Radiology, Thyroid Center, Daerim St Mary's Hospital, Seoul, Korea (J.H.B.); Department of Radiology, Anam Hospital, Korea University School of Medicine, Seoul, Korea (Y.H.L.); Department of Radiology, Severance Hospital, Yonsei University School of Medicine, Seoul, Korea (J.K.); Department of Radiology, Nowon Eulji Hospital, Eulji University School of Medicine, Seoul, Korea (H.S.K.); and Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea (J.S.B.). Received June 5, 2007; revision requested August 8; revision received September 27; accepted November 21; final version accepted December 4.
Address correspondence to W.J.M. (e-mail: mdmoonwj{at}naver.com).
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ABSTRACT
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Purpose: To retrospectively evaluate the diagnostic accuracy of ultrasonographic (US) criteria for the depiction of benign and malignant thyroid nodules by using tissue diagnosis as the reference standard.
Materials and Methods: This study had institutional review board approval, and informed consent was waived. From January 2003 through June 2003, 8024 consecutive patients had undergone thyroid US at nine affiliated hospitals. A total of 831 patients (716 women, 115 men; mean age, 49.5 years ± 13.8 [standard deviation]) with 849 nodules (360 malignant, 489 benign) that were diagnosed at surgery or biopsy were included in this study. Three radiologists retrospectively evaluated the following characteristics on US images: nodule size, presence of spongiform appearance, shape, margin, echotexture, echogenicity, and presence of microcalcification, macrocalcification, or rim calcification. A 
2 test and multiple regression analysis were performed. Sensitivity, specificity, and positive and negative predictive values were obtained.
Results: Statistically significant (P < .05) findings of malignancy were a taller-than-wide shape (sensitivity, 40.0%; specificity, 91.4%), a spiculated margin (sensitivity, 48.3%; specificity, 91.8%), marked hypoechogenicity (sensitivity, 41.4%; specificity, 92.2%), microcalcification (sensitivity, 44.2%; specificity, 90.8%), and macrocalcification (sensitivity, 9.7%; specificity, 96.1%). The US findings for benign nodules were isoechogenicity (sensitivity, 56.6%; specificity, 88.1%; P < .001) and a spongiform appearance (sensitivity, 10.4%; specificity, 99.7%; P < .001). The presence of at least one malignant US finding had a sensitivity of 83.3%, a specificity of 74.0%, and a diagnostic accuracy of 78.0%. For thyroid nodules with a diameter of 1 cm or less, the sensitivity of microcalcifications was lower than that in larger nodules (36.6% vs 51.4%, P < .05).
Conclusion: Shape, margin, echogenicity, and presence of calcification are helpful criteria for the discrimination of malignant from benign nodules; the diagnostic accuracy of US criteria is dependent on tumor size.
© RSNA, 2008
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INTRODUCTION
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At ultrasonography (US), 10%–67% of adults have thyroid nodules, and nearly 50% of the population have thyroid nodules at autopsy (1–4). As determined at fine-needle aspiration cytology, 9.2%–14.8% of nodules identified at clinical examination are diagnosed as malignant (5–7). Thyroid US has been widely used to differentiate benign from malignant nodules and to guide fine-needle aspiration cytology for nodules suspected of being malignant (1,8). US features predictive of malignant nodules include the presence of microcalcifications, hypoechogenicity, and irregular margins, the absence of a halo, a predominantly solid composition, and an intranodular vascularity (5,6,9–14). Some investigators (5,15) suggest that a combination of these US findings provides better diagnostic accuracy than only one of these findings. However, considerable overlap between benign and malignant characteristics has been found in results of some studies (12,14). Sensitivity and specificity of the US findings for malignant thyroid nodules are also variable (1,5,9,11,16,17).
Factors that may affect the findings reported in previous studies include the use of different US equipment, the experience of the radiologists (or physicians), and the different US criteria for identifying a malignancy. In addition to unavoidable interobserver variability during the US examination, there is also the problem of a nonstandardized lexicon for the characterization of thyroid nodules.
The purpose of our study was to retrospectively evaluate the diagnostic accuracy of US criteria for the depiction of benign and malignant thyroid nodules by using tissue diagnosis as the reference standard.
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MATERIALS AND METHODS
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Institutional review board approval was obtained at all participating sites for this retrospective study, and informed consent was waived.
Patients
This retrospective analysis was based on patient data collected from nine university-affiliated hospitals. A total of 8024 consecutive patients with both palpable and nonpalpable nodules who had undergone thyroid US between January 2003 and June 2003 was considered for the study (Fig 1). Only patients who met the following criteria were included: (a) patients who underwent surgery or gun biopsy after thyroid US, (b) patients who underwent fine-needle aspiration cytology at least two times within a 1-year interval for benign thyroid lesions (except for adenomas), and (c) patients who underwent initial fine-needle aspiration cytology and US follow-up (>12 months after fine-needle aspiration cytology) for benign thyroid lesions (except for adenomas). For follicular neoplasms and Hürthle cell neoplasms, patients without a final diagnosis after surgery were excluded from this study. A total of 831 patients (716 women, 115 men) with 849 nodules (360 malignant and 489 benign nodules) was included. The mean patient age was 49.5 years ± 13.8 (standard deviation).
For malignant nodules (n = 360), a pathologic diagnosis was confirmed at surgery (n = 341, 94.7%) or gun biopsy (n = 19, 5.3%). For benign nodules (n = 489), a pathologic diagnosis was confirmed at surgery (n = 173, 35.4%), gun biopsy (n = 68, 13.9%), fine-needle aspiration cytology repeated at least two times within a 1-year interval (n = 182, 37.2%), or fine-needle aspiration cytology and follow-up US (>12 months) (n = 66, 13.5%).
The diagnoses of malignancy at histologic examination included papillary carcinomas (n = 345), follicular carcinomas (n = 9), medullary carcinomas (n = 4), a Hürthle cell carcinoma (n = 1), and a diffuse large B-cell lymphoma (n = 1). Diagnosis of benign lesions at histologic examination included nodular hyperplasia (n = 429), follicular adenoma (n = 46), and thyroiditis (n = 14).
US Examination Technique
All US examinations were performed with either an HDI 5000 (ATL Ultrasound, Bothell, Wash) or Sequoia (Acuson, Mountain View, Calif) instrument equipped with a 5–12-MHz or an 8–15-MHz linear-array transducer. The scanning protocol in all cases included both transverse and longitudinal real-time imaging of the thyroid nodules, with the use of representative Digital Imaging and Communications in Medicine images. Faculty radiologists (W.J.M., S.L.J., J.H.L., D.G.N., J.H.B., Y.H.L., J.K., H.S.K.) specializing in head and neck imaging (n = 10, 4–12 years of experience) performed the examination or supervised a board-certified radiologist who was participating in neuroradiology or head and neck radiology fellowship training.
Retrospective Evaluation
Three experienced head and neck radiologists (reviewers) (W.J.M., S.L.J., and J.H.L., who had 7, 9, and 6 years of experience, respectively, in performing and evaluating thyroid US) reviewed all of the US images in the Digital Imaging and Communications in Medicine format. Initially, two training sessions were held to further establish a baseline consensus in the lexicon for the US criteria. The three reviewers evaluated images of 20 biopsy-proved masses not included in the retrospective study. The three reviewers had no previous knowledge of any of the studies or the original interpretations. Patient clinical histories, previous imaging results, and tissue sampling results were not available to the reviewers. Each of the radiologists was asked to review the studies independently in a single session.
For US of the thyroid nodules, the three reviewers were asked to assess criteria from the published literature (5,10,18) during a consensus meeting to discuss the criteria. The criteria included size (larger than 1 cm, 1 cm or smaller), internal content, the presence of a spongiform appearance, shape, margin, echotexture, echogenicity of solid portion, and calcification (microcalcification, macrocalcification, and/or rim calcification).
The internal content of a nodule was categorized according to the ratio of the cystic portion to the solid portion in the nodule: predominantly solid (<50% cystic) and predominantly cystic (
50% cystic). A spongiform appearance was defined as the aggregation of multiple microcystic components in more than 50% of the volume of the nodule (Fig 2a). The shape of the nodule was categorized as follows: ovoid to round (when the anteroposterior diameter of the nodule was equal to or less than its transverse diameter on a transverse or longitudinal plane), taller than wide (when the anteroposterior diameter of a nodule was longer than its transverse diameter on a transverse or longitudinal plane), or irregular (when a nodule was neither ovoid to round nor taller than wide). The margin of a nodule was categorized as well-defined smooth, spiculated, or ill-defined.
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Figure 2a: US findings of spongiform appearance. (a) Schema of spongiform appearance. (b) Longitudinal US image of benign nodular hyperplasia in a 49-year-old woman shows ill-defined large isoechoic mass (arrows) with spongiform appearance.
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Figure 2b: US findings of spongiform appearance. (a) Schema of spongiform appearance. (b) Longitudinal US image of benign nodular hyperplasia in a 49-year-old woman shows ill-defined large isoechoic mass (arrows) with spongiform appearance.
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Echogenicity of solid portion was assessed in respect to the thyroid parenchyma and strap muscles and was classified as markedly hypoechoic (when a nodule showed a relatively hypoechoic pattern in regard to the adjacent strap muscle), hypoechoic (when a nodule showed a relatively hypoechoic pattern in regard to the normal thyroid parenchyma), isoechoic (when a nodule showed an isoechoic pattern in regard to the normal thyroid parenchyma), or hyperechoic (when a nodule showed a relatively echogenic pattern in regard to the normal thyroid parenchyma).
Calcification was assessed in respect to its size and was classified as microcalcification (when there were tiny, punctate echogenic foci of 1 mm or less either with or without posterior shadowing), macrocalcification (when punctate echogenic foci were larger than 1 mm in size), or rim calcification (when a nodule had a peripheral curvilinear or egg-shell calcification).
Statistical Analysis and Reference Standard
Statistical analysis was performed by using a software package (SPSS, version 12.0 for Windows; SPSS, Chicago, Ill). Each of the US characteristics was analyzed to determine its association with a benign versus a malignant tissue diagnosis. For each reader, the relevant findings were compared with the tissue diagnosis (reference standard) to determine sensitivity, specificity, negative predictive value, and positive predictive value. A significant difference was defined as P less than .05. A 2 test and a Fisher exact test were used for comparison of categoric variables, and a Student t test was used for comparison of quantitative variables (age and tumor size). In addition, multiple logistic regression analysis with a forward stepwise method for selection of significant variables was performed to determine independent US predictors for malignancy from the US characteristics that showed statistical significance (P < .05).
Interobserver agreement was assessed for each of the US characteristics by using the Cohen 
statistic. The guidelines of Landis and Koch (19) were followed for the interpretation of values: 0.00–0.20 indicated slight agreement; 0.21–0.40, fair agreement; 0.41–0.60, moderate agreement; 0.61–0.80, substantial agreement; and 0.80–1.00, almost perfect agreement.
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RESULTS
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US Characteristics of All Nodules
The size of nodules ranged from 2.7 to 64.0 mm (mean size, 16.9 mm ± 10.8). The mean maximal diameter of the malignant nodules (13.1 mm ± 0.86) was significantly smaller than that of the benign nodules (19.7 mm ± 11.3) (P < .001).
A predominantly solid component was observed in the majority of benign and malignant nodules (87.1% vs 98.3%, P < .001) (Table 1). The statistically significant features for the depiction of a benign nodule were an ovoid-to-round shape, a well-defined smooth margin, isoechogenicity, and a spongiform appearance (Figs 2b, 3). The statistically significant features for the depiction of a malignant nodule were a taller-than-wide shape, a spiculated margin, marked hypoechogenicity, hypoechogenicity, microcalcification, and macrocalcification (Figs 4–7). Despite statistical significance, hypoechogenicity was found in 33.7% of benign nodules and 46.1% of malignant nodules. Although an ovoid-to-round shape and a well-defined smooth margin were found more frequently in benign nodules, the number of malignant nodules with the same features was substantial (57.8% and 32.5%, respectively). We found no significant difference for irregular shape, ill-defined margin, echotexture, hyperechogenicity, and rim calcification.
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Figure 3: Transverse US image of follicular adenoma in a 34-year-old woman shows a well-defined smooth, ovoid-shaped, and hypoechoic nodule. There are no micro- or macrocalcifica-tions.
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Figure 4: Transverse US image of papillary carcinoma in a 46-year-old woman shows an ill-defined, taller-than-wide shaped, and hypoechoic nodule (arrow). There are no micro- and macrocalcifications. The taller-than-wide shape suggests a malignant nodule.
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A multiple logistic regression analysis was performed to determine independent US predictors for malignancy (Table 2). Five criteria showed a significant association with thyroid cancer (P < .05). The presence of a spongiform appearance had a negative association with thyroid cancer, which signifies an unlikely malignancy.
US Characteristics of Nodules according to Size
To evaluate the relationship between nodule size and US features, we chose a cutoff diameter of 10 mm that has been used as part of the criteria for a microcarcinoma in a pathologic diagnosis (20). Malignant nodules with a diameter of 10 mm or smaller showed microcalcification less frequently than did nodules with a larger diameter (36.6% vs 51.4%; 2 test, P = .005). Other US findings suggestive of malignancy as described above showed no significant difference between malignant nodules smaller than 10 mm and those larger than 10 mm. In contrast, benign nodules with a diameter of 10 mm or smaller showed a spiculated margin (16.5% vs 5.8%, P = .001) and marked hypoechogenicity (14.0% vs 6.0%, P = .006) more frequently than did nodules with a larger diameter. The frequency of benign nodules with marked hypoechogenicity or hypoechogenicity was 62.5% in the subgroup with a smaller diameter and 35.6% in the subgroup with a larger diameter (P < .001).
When US features suggestive of a benign nodule (an ovoid-to-round shape, a well-defined smooth margin, isoechogenicity, and a spongiform appearance) were compared, no significant difference in their frequency was found between malignant nodules smaller than 10 mm and those larger than 10 mm. In contrast, benign nodules larger than 10 mm had more isoechogenicity (62.6% vs 35.5%, P < .001) and a well-defined smooth margin (78.8% vs 65.4%, P < .001) compared with nodules 10 mm or smaller.
Diagnostic Accuracy of US Criteria for Depiction of Malignant Nodules
No single US feature suggestive of malignancy had an overall diagnostic accuracy that exceeded 75.0% (Table 3). When a criterion for nodule echogenicity included hypoechogenicity as well as marked hypoechogenicity, this criterion showed a relatively high sensitivity but a low specificity (58.5%). In contrast, presence of the other findings (taller-than-wide shape, spiculated margin, marked hypoechogenicity, or microcalcification) was very specific (90.8%–92.2%) but not sensitive (40.0%–48.3%). The presence of a macrocalcification had a high specificity (96.1%) but a low sensitivity (9.7%). When the presence of one or more of the above mentioned malignant findings was chosen as a criterion for malignancy, the overall accuracy increased to 78.0%.
The diagnostic accuracy of the US features was evaluated separately for nodules smaller than 10 mm and those larger than 10 mm (Table 4). The US features suggestive of malignancy showed a higher specificity and a lower sensitivity for larger nodules than for smaller nodules. For smaller nodules, the US feature of hypoechogenicity including marked hypoechogenicity showed a comparatively high sensitivity (90.9%) but a low specificity (37.4%). The diagnostic value of microcalcification for cancer diagnosis was higher for larger nodules (51.4% sensitivity and 91.6% specificity) than for smaller nodules (36.6% sensitivity and 87.9% specificity). For benign nodules, the combination of nodule isoechogenicity with a spongiform appearance had the highest specificity of 100% (Table 5).
Reviewer Agreement of US Characteristics of Thyroid Nodules
The three reviewers had a moderate or higher agreement for internal content, spongiform appearance, and presence of microcalcifications (Table 6). A fair agreement was reported for shape, margin, echotexture, and echogenicity.
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DISCUSSION
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In our study, we achieved, with reasonable interreviewer reliability, a diagnostic accuracy up to 78.0% when the presence of one of the malignant US findings was applied for a diagnosis of malignant thyroid nodules.
Traditionally, a predominantly solid component is regarded as being suggestive of a malignant nodule rather than a benign nodule (1,11). In some reports, however, 60%–83% of benign nodules were predominantly solid (12,14). In our study, most of the benign nodules, as well as the malignant nodules, were predominantly solid. Therefore, a predominantly solid component alone cannot be a useful criterion for the differentiation of malignant from benign nodules.
Our findings support previous study results (13,16) that suggest a taller-than-wide shape is very specific for differentiating malignant thyroid nodules from benign ones. This result conveys the fact that malignant nodules (taller than wide) grow across normal tissue planes, while benign nodules grow parallel to normal tissue planes (13,16,21).
We categorized the tumor margin into three subtypes: well-defined smooth, spiculated, and ill-defined margin. Results of earlier reports (5,22) have suggested that blurred or ill-defined nodular margins favor a diagnosis of malignancy. However, with the development of high-frequency transducer US techniques, a previously described ill-defined margin could actually be a spiculated margin with sharp demarcation or a poorly defined margin in which the tumor cannot be discriminated from the normal parenchyma. When the marginal tumor infiltration of malignancy is minimal, it can be seen as an ill-defined margin. In addition, benign thyroid nodules are known to be incompletely encapsulated and poorly marginated and can also merge with the normal tissue (23). Therefore, we hypothesized that a spiculated margin is suggestive of malignancy, while an ill-defined margin can be seen in both benign and malignant nodules. This hypothesis is supported by our findings.
Although we found that the frequency of hypoechogenicity was significantly different between benign and malignant nodules (P = .001), we observed in detail that marked hypoechogenicity was highly specific for diagnosing malignant nodules, whereas hypoechoic nodules included nearly 50% of the benign nodules and the majority of the malignant nodules. For smaller thyroid nodules, the majority of benign nodules (62.5%) were hypoechoic in regard to the normal parenchyma. These findings are in accordance with previous studies (5,12,16) that were on a smaller scale. Marked hypoechogenicity, as suggested previously (16), can be a more specific and more reliable criterion for a malignant thyroid nodule than hypoechogenicity in a broader sense.
In our study, the presence of any micro- or macrocalcification increased the risk of malignancy by an odds ratio of 4.599 and 2.792, respectively. In results of a previous study (1), the presence of a microcalcification in a predominantly solid nodule increased cancer risk by threefold, and coarse macrocalcifications increased cancer risk twofold, compared with predominantly solid nodules without any calcifications. Microcalcifications have a high predictive value (41.8%–94.2%) but a low sensitivity (26.1%–59.1%) (5,9,11,16,24). Microcalcifications correspond pathologically to calcified psammoma bodies that are typical of papillary cancer (25,26). Macrocalcifications or coarse calcifications are related to fibrosis and degeneration (24,27). Benign nodules have coarse calcifications, especially with a long disease duration (22,28,29).
There has been no clear size criterion for determining whether a calcification is a micro- or macrocalcification. Thus, we arbitrarily classified each calcification as a micro- or macrocalcification by using the cutoff value of 1 mm. Accordingly, this criterion may not represent the exact pathologic condition. In our study, the incidence of a macrocalcification is rather uncommon (9.7% of malignant nodules and 3.9% of benign nodules). Our study included only patients who had undergone at least a surgical biopsy and a repeated biopsy. Therefore, a substantial number of benign thyroid nodules with macrocalcification may have been excluded inadvertently. The presence of a rim calcification showed no statistical significance in the differentiation of a malignant nodule from a benign nodule. It has been reported that a specific type of rim calcification suggests the presence of a malignancy (30). The relationship of a rim calcification with malignancy has yet to be elucidated (1).
Our results suggest that a spongiform appearance and isoechogenicity are US indicators for benign nodules. Previously, a nodule seen with a "honeycomb" pattern, which is characterized by multiple cystic spaces separated by thin septae, has been regarded as a benign nodule (22,23). However, there has been no clear evidence for this finding and no clear consensus on the use of this terminology. We defined a spongiform appearance as a nodule containing microcystic components occupying more than half of the entire volume. This US feature is specific, especially in combination with the feature of isoechogenicity.
According to the nodule size, different patterns of the US features have been observed in this study. A lower frequency of microcalcification in microcarcinomas suggests that microcalcification is not a major predictor of malignancy in nodules 1 cm or smaller. Although other findings such as marked hypoechogenicity, taller-than-wide shape, and spiculated margin are slightly more frequent in smaller malignant nodules, they are also more frequent in smaller benign nodules. Accordingly, the false-positive rate of depiction of a malignant nodule could be increased in smaller nodules.
In this study, the overall sensitivity of thyroid US for depicting a malignant nodule was 83.3%. The majority (75%–80%) of new cases of thyroid cancer are papillary carcinomas. Other histologic types include follicular (10%–20%), medullary (3%–5%), and anaplastic (1%–2%) cancers (3,9,30,31). The malignant US findings are the features that suggest a papillary carcinoma, which makes sense considering the major proportion of papillary carcinomas in our cases. US findings of a follicular carcinoma or follicular variant of a papillary carcinoma, as well as other malignancies such as a medullary carcinoma and lymphoma, are somewhat different from those of a typical papillary carcinoma (31–36).
The majority (80%–85%) of papillary carcinomas that comprise most thyroid carcinomas are regarded as low-risk malignancies with a 99% survival rate at 20 years after surgery (1,37). With regard to questioning the survival benefit of standard total thyroidectomy with adjuvant radioiodine treatment in such low-risk groups (1,37–39), some investigators do not recommend US-guided biopsy in nodules 1 cm or smaller, even if they have US findings suggestive of a malignancy. In contrast, other investigators (16,40,41) reported that even thyroid nodules smaller than 1 cm may show early lymph node metastasis or extranodal invasion and therefore require US-guided biopsy if any malignant-appearing US finding is present. With the presence of one of the US findings suggesting a malignant nodule, the overall sensitivity was about 80% in nodules 1 cm or larger. A false-negative rate of 20% is not trivial, even if the diagnosed cancer is low risk. When we define the echogenicity criterion in a broader sense (ie, hypoechogenicity plus marked hypoechogenicity) in thyroid nodules 1 cm larger, we could enhance the sensitivity of the US finding (91.9%) with sacrifice of the specificity. Maybe one can choose the echogenicity criterion in a broader sense (ie, hypoechogenicity plus marked hypoechogenicity) for a larger nodule under certain circumstances, such as those in a high-risk group. On the other hand, we feel that a sensitivity of 85% in a thyroid nodule 1 cm or smaller is acceptable. We feel that different strategies for US diagnosis are needed for nodules with different sizes.
In assessment of the US findings, the nodule shape, margin, echotexture, and echogenicity showed only fair agreement. This relatively low interreviewer reliability may be because of the retrospective study design. In spite of a training session before the evaluation, the assessment of stored images rather than real-time images can confound one's judgment of the characteristics of each nodule.
There were some limitations of our study. The evaluation of cases was retrospective, and there was unavoidable selection bias. The retrospective study design prevented us from evaluating US findings in real time, which might have influenced the evaluation of the interpreters. For instance, patients with obviously benign findings at US usually did not undergo biopsy or surgery, which might have resulted in relatively fewer benign masses in our study than expected in daily practice. These limitations could be overcome by conducting a large-scale prospective study in the near future.
In conclusion, US criteria for the discrimination of malignant from benign nodules are taller-than-wide shape, spiculated margin, marked hypoechogenicity, and the presence of micro- or macrocalcifications, of which the diagnostic accuracy may be dependent on tumor size; furthermore, isoechogenicity of the nodule in conjunction with a spongiform appearance are reliable US criteria for benign nodules.
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ADVANCES IN KNOWLEDGE
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- US criteria for malignant nodules are shape (taller than wide), margin (spiculated), echogenicity (marked hypoechogenicity), and the presence of calcifications (micro- or macrocalcifications), with accuracy ranging from 59.5% to 73.4%.
- The diagnostic accuracy of the US criteria for malignancy is dependent on tumor size.
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IMPLICATION FOR PATIENT CARE
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- Application of US criteria for the differentiation of malignant from benign nodules may help in accurate diagnosis of thyroid nodules.
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ACKNOWLEDGMENTS
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We thank Seonwoo Kim, PhD, from the Biostatistics Unit of Samsung Biomedical Research Institute for her statistical advice.
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FOOTNOTES
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Author contributions: Guarantor of integrity of entire study, W.J.M.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; manuscript final version approval, all authors; literature research, W.J.M., S.L.J., J.H.L., J.K.; clinical studies, all authors; statistical analysis, W.J.M., S.L.J.; and manuscript editing, W.J.M., J.H.L., D.G.N., J.H.B., Y.H.L.
Authors stated no financial relationship to disclose.
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ABSTRACT
INTRODUCTION
